Solve, then check algebraically and graphically. 9x-3=78

If its acceleration is constant, then it is equal to the jet's average velocity, given by

[tex]a=a_{\rm ave}=\dfrac{\Delta v}{\Delta t}[/tex]

Then it takes

[tex]17.7\dfrac{\rm m}{\mathrm s^2}=\dfrac{233\frac{\rm m}{\rm s}-119\frac{\rm m}{\rm s}}{\Delta t}\implies\Delta t=\boxed{6.44\,\mathrm s}[/tex]

Answer:

The time taken by the jet is 6.44 seconds.

Step-by-step explanation:

It is given that,

Acceleration of the jet, [tex]a=17.7\ m/s^2[/tex]

Initial velocity of the jet, u = 119 m/s

Final velocity of the jet, v = 233 m/s

Acceleration of an object is given by :

[tex]a=\dfrac{v-u}{t}[/tex]

[tex]t=\dfrac{v-u}{a}[/tex]

[tex]t=\dfrac{233-119}{17.7}[/tex]

t = 6.44 seconds

So, the time taken by the jet is 6.44 seconds. Hence, this is the required solution.

Answer:

  C'(4, 4)

Step-by-step explanation:

We assume dilation is about the origin, so all coordinates are multiplied by the scale factor:

  C' = 2C = 2(2, 2) = (4, 4)

Answer:

0.889

Step-by-step explanation:

I think it is multiplied.

10 *9 = 90

which is the total number of ways you can draw 2 cards without replacement.

I think it is easier to figure out how many possibilities there are over 62 and go from there.

10*9

10*8

10*7

===========

9*8

9*7

So there are 5 combinations that are over 62. There are 5 more possibilities because you could draw them in the reverse order

9 * 10

8 * 10

7 * 10  

8* 9

7 * 9

In all there are 10 ways of drawing numbers that are over 62

So what is the probability of drawing 2 cards above 62?

10/90 = 1/9 = 0.111

Therefore, there must be a probability of 1 - 0.111 for under 62 = 0.889

Answer:

  (y² +1)/y

Step-by-step explanation:

Invert the denominator fraction and multiply. Factor the difference of squares.

[tex]\displaystyle\frac{\left(\frac{6y^2-6}{8y^2+8y}\right)}{\left(\frac{3y-3}{4y^2+4}\right)}=\frac{6(y^2-1)}{8y(y+1)}\cdot\frac{4(y^2+1)}{3(y-1)}\\\\=\frac{24(y+1)(y-1)(y^2+1)}{24y(y+1)(y-1)}=\frac{y^2+1}{y}[/tex]

Answer:

Step-by-step explanation:

As the value of a increases, the radical function sweeps out higher, increasing the range of the function.  The k value moves it up or down.  A "+k" moves up (for example, +3 moves the function up 3 from the origin).  The h value moves it side to side.  A positive h value moves to the right and a negative h value moves to the left.  For example, √x-3 moves 3 to the right and √x+3 moves 3 to the left.

In summary, a and k affect the range of the function, k being the "starting point" and a being the "ending point"; h affects the domain of the function.

Answer:

=20s³+50s²+32s+6

Step-by-step explanation:

We multiply each of the term in the initial expression by the the second expression as follows:

4s(5s²+10s+3)+2(5s²+10s+3)

=20s³+40s²+12s+10s²+20s+6

Collect like terms together.

=20s³+50s²+32s+6

Answer:

E) -3, 5

Step-by-step explanation:

x – 15 / x = 2

x^2 - 15 = 2x

x^2 - 2x - 15 = 0

(x - 5)(x + 3) = 0

x - 5 = 0; x = 5

x + 3 = 0; x = -3

Solutions: -3, 5

For this case we must solve the following equation:

[tex]x- \frac {15} {x} = 2[/tex]

We manipulate the equation algebraically:

[tex]\frac {x ^ 2-15} {x} = 2\\x ^ 2-15 = 2x\\x ^ 2-2x-15 = 0[/tex]

To solve, we factor the equation. We must find two numbers that when multiplied by -15 and when summed by -2. These numbers are:

+3 and -5.

[tex](x + 3) (x-5) = 0[/tex]

So, the roots are:

[tex]x_ {1} = - 3\\x_ {2} = 5[/tex]

Answer:

Option E

Answer:

  x = 117°, 297°

Step-by-step explanation:

Subtract 1 from both sides of the equation and you have ...

  tan(x) = -2

Then the arctangent function tells you ...

  x = arctan(-2) ≈ 116.5651°, 296.5651°

  x ≈ 117° or 297°

Answer:

b. y+7=5x

Step-by-step explanation:

a. 1-3x^2     is a quadratic

b. y+7=5x    is a linear function:  y = 5x - 7

c. x^3 + 4 = y   is a cubic function

d. 9(x^2-y) = 3    is a quadratic function

e.y-x^3=8   is a cubic function

Answer:

Option 4: (x+1)^2+(y-1)^2 = 16

Step-by-step explanation:

The radius of the given circle in attached picture is: 4 units

The center is denoted by (h,k) = (-1,1)

So,

The standard form of equation with center at (h,k) and radius r

(x-h)^2 + (y-k)^2 = r^2

Putting the values

(x-(-1))^2 + (y-1)^2 = 4^2

(x+1)^2+(y-1)^2 = 16

Hence option number 4 is correct ..

Answer:

Step-by-step explanation:

f(10) = 120 tells you that after x = 10 minutes, the coffee is 120 degrees

The statement f(10)=120 indicates that after 10 minutes, the coffee's temperature is 120 degrees Fahrenheit.

When we see an equation such as f(10)=120, it tells us that after 10 minutes, the temperature of the coffee has cooled down to 120 degrees Fahrenheit. The function f(x) describes the temperature of the coffee after x minutes, so the specific point f(10)=120 provides us with a snapshot of the temperature at that particular time.

Answer:

Time taken by Doreen is 6 hours and speed is 10 miles per hour.

Time taken by Sue is 4 hours and speed is 20 miles per hour.

Step-by-step explanation:

Let the speed of Doreen be x

According to the question  speed of Sue   is = x+10

time  taken By Sue to cover 80 miles = [tex]\frac{80}{x+10}[/tex]

time taken by Doreen to travel 60 miles = [tex]\frac{60}{x}[/tex]

According to question Sue take two hours less than Doreen takes

therefore

[tex]\frac{60}{x}[/tex] - [tex]\frac{80}{x+10}[/tex] =2

[tex]\frac{60(x+10)-80x}{x(x+10)}[/tex] =2

60(x+10) -80x = 2(x(x+10)

60x+600-80x = [tex]2x^2+20x\\[/tex]

simplifying it ,we get

[tex]2x^2+40x-600=0\\[/tex]

Dividing both sides by 2 ,we get

[tex]x^2+20x-300=0\\[/tex]

solving it for x ,we get

(x+30)(x-10) =0

x =-30 which is not possible

x =10 miles per hour

Speed of Doreen = 10 miles per hour

Speed of Sue = 10+10 = 20 miles per hour

Time taken by Doreen = 60 divided by 10 = 6 hours

Time taken  by Sue = 80 divided by 20 = 4 hours

In conclusion, Doreen travels at a speed of 30 mph, taking her 4 hours to travel 60 miles. Sue, on the other hand, travels at a speed of 40 mph, taking her 2 hours to travel 80 miles.

This problem is a classic example of distance, rate, and time relations in mathematics. Let's start by denoting Sue's speed as x mph, the Doreen's speed would then be x-10 mph. We know that time is equal to distance divided by speed. So, the time it takes Sue to travel 80 miles would be 80/x hours and the time it takes Doreen to travel 60 miles would be 60/(x-10) hours. The question states that Sue's travel time is 2 hours less than Doreen's. Therefore, we can form the equation: 60/(x-10) = 80/x + 2. Solving this equation, we find that x equals 40 mph, which is Sue's speed and Doreen's speed is 30 mph. Consequently, the time it takes Sue to travel 80 miles is 2 hours and for Doreen to travel 60 miles is 4 hours.

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Answer:

a. 0.17

Step-by-step explanation:

Total number of light bulbs = 8

The probability that each individual light bulb works = 0.8

The working of light bulbs is independent of each other, this means one light bulb does not influence the other light bulbs.

We need to calculate the probability that all eight of the light bulbs work. Since the light bulbs work independently, the overall probability of independent events occurring together is the product of their individual probabilities. Therefore,

Probability that all eight of the light bulbs work = 0.8 x 0.8 x 0.8 x 0.8 x 0.8 x 0.8 x 0.8 x 0.8

= [tex](0.8)^{8}[/tex]

= 0.16777216

≈ 0.17

Thus, option a gives the correct probability that all eight of the light bulbs work

You can use binomial distribution, and thus, its probability function to find the needed probability.

The probability that all eight of the light bulbs work is 0.167

Binomial distributions consists of n independent Bernoulli trials.

Bernoulli trials are those trials which end up randomly either on success (with probability p) or on failures( with probability 1- p = q (say))

Suppose we have random variable X pertaining binomial distribution with parameters n and p, then it is written as

[tex]X \sim B(n,p)[/tex]

The probability that out of n trials, there'd be x successes is given by

[tex]P(X =x) = \: ^nC_xp^x(1-p)^{n-x}[/tex]

Since all the light bulbs' working is independent, and each bulb's chance of working is 0.8 and there are 8 bulbs, thus,

n = 8

p = 0.8

and Let X be a random variable tracking how many out of 8 bulbs are working, then we have:

[tex]X \sim B(8, 0.8)[/tex]

Then, the needed probability is P(X = 8) (since we need to know probability that all 8 bulbs will work)

By using the probability mass function of binomial distribution, we get:

[tex]P(X =x) = \: ^nC_xp^x(1-p)^{n-x}\\P(X = 8) = \:^8C_8(0.8)^8(1-0.8)^{8-8} = 1 \times (0.8)^8 \times 1 \approx 0.167[/tex]

Thus,

The probability that all eight of the light bulbs work is 0.167

Learn more about binomial distribution here:

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Answer:

[tex]50xy[/tex] and [tex]40x^2[/tex].

Step-by-step explanation:

The given polynomial is [tex]36x^3-22x^2-144x[/tex].

The prime factorization of each term are;

[tex]36x^2=2^2\times 3^2\times x^3[/tex]

[tex]-22x^2=-2\times 11\times x^2[/tex]

[tex]-144x=-2^4\times 3^2\times x[/tex]

The greatest common factor of these three terms is [tex]2x[/tex].

Now observe that:

The GCF of [tex]2x[/tex] and 11 is 1

The GCF of [tex]2x[/tex] and 50xy is 2x

The GCF of [tex]2x[/tex] and [tex]40x^2[/tex] is 2x

The GCF of [tex]2x[/tex] and 24 is 2

The GCF of [tex]2x[/tex] and 10y is 2

The correct options are [tex]50xy[/tex] and [tex]40x^2[/tex].

Answer:

Component form of u is (-18,13)

The magnitude of u is 22.2

Step-by-step explanation:

The component form of a vector is an ordered pair that describe the change is x and y values

This is mathematically expressed as (Δx,Δy) where Δx=x₂-x₁ and Δy=y₂-y₁

Given ;

Initial points of the vector as (14,-6)

Terminal point of the vector as (-4,7)

Here x₁=14,x₂=-4, y₁=-6 ,y₂=7

The component form of the vector u is (-4-14,7--6) =(-18,13)

Finding Magnitude of the vector

║u=√(x₂-x₁)²+(y₂-y₁)²

║u=√-18²+13²

║u=√324+169

║u=√493

║u=22.2

Answer:

2 gallons

Step-by-step explanation:

At this speed, the car uses 1 gallon of fuel for a distance of 25 miles.

We need the number of miles the car travels in 75 minutes to find the amount of fuel it uses.

75 minutes * (1 hour)/(60 minutes) = 1.25 hours

speed = distance/time

distance = speed * time

distance = 40 miles/hour * 1.25 hours = 50 miles

In 75 minutes, at 40 mph, the car travels 50 miles.

(1 gal)/(25 miles) = x/(50 miles)

x = 2 gal

Answer: 2 gallons

The car will use 2 gallons of fuel when traveling at a constant speed of 40 miles per hour for 75 minutes.

To find the number of gallons of fuel used when the car travels at a constant speed of 40 miles per hour for 75 minutes, we can use the formula:

Gallons of fuel used = (Distance traveled in miles) / (Miles per gallon)

Since the car travels at a constant speed of 40 miles per hour, it covers a distance of 40 miles in 1 hour. Therefore, in 75 minutes it will travel 40 miles * (75 minutes / 60 minutes per hour) = 50 miles.

Now, we can calculate the number of gallons of fuel used: Gallons of fuel used = 50 miles / 25 miles per gallon = 2 gallons.

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[tex]

\Sigma_{n=1}^{4}-2\cdot(-3)^{n-1} \\

(-2)(-3)^{1-1}+(-2)(-3)^{2-1}+(-2)(-3)^{3-1}+(-2)(-3)^{4-1} \\

-2+6-18+54 \\

\boxed{40}

[/tex]

So the answer is C,

[tex]\Sigma_{n=1}^{4}-2\cdot(-3)^{n-1}=40[/tex]

Hope this helps.

r3t40

The sum of the finite geometric series (-2)(-3)ⁿ⁻¹ for n=1 to n=4 is 40, calculated using the geometric series sum formula.So,option C is correct.

The sum of a finite geometric series with a general term given as (-2)(-3)ⁿ⁻¹ where 'n' ranges from 1 to 4. To find the sum of a geometric series, we need to identify the first term (a) and the common ratio (r), and then use the formula Sₙ = a(1 - rⁿ) / (1 - r), where n is the number of terms.

The first term of the series can be found by substituting n = 1 into the general expression, yielding a = (-2)(-3)¹⁻¹ = -2. The second term, with n = 2, is (-2)(-3)²⁻¹ = -6(-3) = 18, indicating a common ratio of -3.

Thus, the sum of the series for the first four terms can be calculated as:

S₄ = (-2)(1 - (-3)⁴) / (1 - (-3))

S₄= (-2)(1 - 81) / (1 + 3)

S₄= (-2)(-80) / 4

S₄ = 160 / 4

S₄ = 40

Therefore, the sum of the given geometric series is 40.

Answer:

[tex]\frac{\pi }{6}[/tex]

Step-by-step explanation:

The volume of a sphere is [tex]\frac{4}{3} \pi r^{3}[/tex]

Just plug in 1/2 for r

[tex]\frac{4}{3} \pi (\frac{1}{2}) ^{3}[/tex]

The answer is [tex]\frac{\pi }{6}[/tex]

Answer:

Answer would be 9y+36

Step-by-step explanation:

Because if you distribute the 9 inside the parenthesis, you'd get

9*y=9y and 9*4=36

so 9y+36

Hope my answer was helpful to you!

Final answer:

The Distributive Property is used to rewrite the expression 9(y + 4) as 9y + 36 by multiplying 9 by each term inside the parentheses.

Explanation:

To use the Distributive Property to rewrite the expression 9(y + 4), we would distribute the number 9 to both y and 4 inside the parentheses. This means we multiply 9 by y and then multiply 9 by 4, combining the results with the addition operations between them.

Using the distributive property, we get:

9 times y = 9y

9 times 4 = 36

So, the expression will be rewritten as:

9y + 36

Therefore, by distributing the 9, we have turned the original expression into a sum of two terms, which are a number, variable, or a product/quotient of numbers and/or variables separated by + or - signs. In this case, the terms are 9y and 36.

Answer:

[tex]AC=4.3\ in[/tex]

Step-by-step explanation:

see the attached figure to better understand the problem

we know that

The triangle AOC is an isosceles triangle

OA=OC=5/2=2.5 in -----> the radius of the circle

∠AOC=180°-60°=120°

∠CAO=∠ACO=120°/2=60°

Applying the law of cosines find the length of the chord AC

[tex]AC^{2}=OA^{2}+OC^{2}-2(OA)(OC)cos(120\°)[/tex]

substitute

[tex]AC^{2}=2.5^{2}+2.5^{2}-2(2.5)(2.5)cos(120\°)[/tex]

[tex]AC^{2}=18.75[/tex]

[tex]AC=4.3\ in[/tex]

The maximum difference in the lengths of the radii is 1/2.

To solve this problem, let's denote the radius of the smaller circle as ( r ) and the radius of the larger circle as ( R ). We're given that [tex]\( r + R = 10 \)[/tex].

The area of a circle is given by the formula [tex]\( A = \pi r^2 \)[/tex], where ( r ) is the radius.

We want the absolute difference in the areas of the two circles to be less than or equal to [tex]\( 5\pi \)[/tex]. So, we can set up the following inequality:

[tex]\[ |(\pi R^2) - (\pi r^2)| \leq 5\pi \][/tex]

[tex]\[ |(\pi (10-r)^2) - (\pi r^2)| \leq 5\pi \][/tex]

Expanding and simplifying:

[tex]\[ |(100\pi - 20\pi r + \pi r^2) - (\pi r^2)| \leq 5\pi \][/tex]

[tex]\[ |100\pi - 20\pi r| \leq 5\pi \][/tex]

[tex]\[ 100 - 20r \leq 5 \][/tex]

[tex]\[ 100 - 5 \leq 20r \][/tex]

[tex]\[ 95 \leq 20r \][/tex]

[tex]\[ \frac{95}{20} \leq r \][/tex]

[tex]\[ r \geq \frac{19}{4} \][/tex]

So, the maximum difference in the lengths of the radii is when [tex]\( r = \frac{19}{4} \)[/tex] and [tex]\( R = 10 - r = 10 - \frac{19}{4} = \frac{21}{4} \)[/tex].

The maximum difference in the lengths of the radii is [tex]\( \frac{21}{4} - \frac{19}{4} = \frac{2}{4} = \frac{1}{2} \)[/tex].

Answer:

(A)

Step-by-step explanation:

Answer:

Option A is correct.

Step-by-step explanation:

Given  : [tex]f(x) =2^{x}[/tex] and [tex]g(x) =2^{x+4}[/tex].

To find : How will the graph of g(x) differ from the graph of f(x).

Solution : We have given that  

[tex]f(x) =2^{x}[/tex] and g(x)   [tex]g(x) =2^{x+4}[/tex]

By the transformation Rule : If f(x) →→ f(x +h) if mean graph of function shifted to left by h units .

Then  graph of [tex]g(x) =2^{x+4}[/tex] is the graph of [tex]f(x) =2^{x}[/tex] is shifted by 4 unt left.

Therefore, Option A is correct.

Check the picture below.

Answer:

x = 60°

Step-by-step explanation:

From ΔOPQ,

∠OPQ = 120°   [ angle at the center inscribed by arc PQ ]

PQ ≅ OQ

so opposite angles to PQ and OQ will be equal

∠OPQ  ≅ ∠OQP

∠OPQ + ∠OQP + ∠POQ = 180°

∠OPQ + ∠OPQ + 120 = 180°

2∠OPQ = 180 - 120 = 60°

∠OPQ = 30°

Since radius OP is perpendicular to tangent.

so ∠OPQ + Y = 90°

y + 30° = 90°

y = 90 - 30 = 60°

Answer x = 60°

Answer:

Given:

Diameter of lake = 2 miles

∴ [tex]Radius = \frac{Diameter}{2}[/tex] = 1 miles  

The circumference of the lake can be computed as :

Circumference = 2πr

Circumference = 2×3.14×1 = 6.28 miles

This circumference is the total distance traveled by Johanna.

We are give the speed at which Johanna jogs, i.e. Speed = 3 miles/hour

∴ Time taken by Johanna to jog around the lake is given as :

[tex]Time = \frac{Distance}{Speed}[/tex]

Time = 2.093 hours

∴ The correct option is (c.)

Answer:

The dimensions of the brand name television are [tex]26\frac{2}{3}\ in[/tex] by  [tex]66\frac{2}{3}\ in[/tex]

Step-by-step explanation:

we know that

The generic version was based on the brand name and was 3/5 the size of the brand name

Let

x----> the length of the size of the brand name

y----> the width of the size of the brand name

Find the length of the size of the brand name

we know that

[tex]40=\frac{3}{5}x[/tex] -----> equation A

Solve for x

Multiply by 5 both sides

[tex]5*40=3x[/tex]

Rewrite and divide by 3 both sides

[tex]x=200/3\ in[/tex]

Convert to mixed number

[tex]200/3=(198/3)+(2/3)=66\frac{2}{3}\ in[/tex]

Find the width of the size of the brand name

we know that

[tex]16=\frac{3}{5}y[/tex] -----> equation B

Solve for y

Multiply by 5 both sides

[tex]5*16=3y[/tex]

Rewrite and divide by 3 both sides

[tex]x=80/3\ in[/tex]

Convert to mixed number

[tex]80/3=(78/3)+(2/3)=26\frac{2}{3}\ in[/tex]

Answer:

Length of arc AB is,

= 2πr (angle between AB) /360

=2×3.14×90/360

=1.57 cm

For this case we have that by definition, the arc length of a circle is given by:

[tex]AL = \frac {x * 2 \pi * r} {360}[/tex]

Where:

x: Represents the angle between AB. According to the figure we have that x = 90 degrees.

[tex]r = 7.9 \ cm[/tex]

So:

[tex]AL = \frac {90 * 2 \pi * 7.9} {360}\\AL = \frac {90 * 2 * 3.14 * 7.9} {360}\\AL = \frac {4465,08} {360}\\AL = 12.403[/tex]

Answer:

[tex]12.4\ cm[/tex]

Answer:

Option D

Step-by-step explanation:

We have the following variable definitions:

sofas: x

pillows: y

Pillows come in pairs so we have 2y pillows

The total order for all the possible combinations is:

[tex]x+2y[/tex]

The wholesaler requires a minimum of 4 items in each order from its retail customers. This means the retailers can order 4 or more.

Therefore the inequality is:

[tex]x+2y\ge4[/tex]

To graph this inequality, we graph the corresponding linear equation, [tex]x+2y=4[/tex]  with a solid line and shade above.

The correct choice is D

See attachment

Answer:

So we have the two real points (3/2 , 9/2)  and (-1,2).

(Question: are you wanting to use the possible rational zero theorem? Please let me know if I didn't answer your question.)

Step-by-step explanation:

y=2x^2

y^2=x^2+6x+9

is the given system.

So my plain here is to look at y=2x^2 and just plug it into the other equation where y is.

(2x^2)^2=x^2+6x+9

(2x^2)(2x^2)=x^2+6x+9

4x^4=x^2+6x+9

I'm going to put everything on one side.

Subtract (x^2+6x+9) on both sides.

4x^4-x^2-6x-9=0

Let's see if some possible rational zeros will work.

Let' try x=-1.

4-1+6-9=3+(-3)=0.

x=-1 works.

To find the other factor of 4x^4-x^2-6x-9 given x+1 is a factor, I'm going to use synthetic division.

-1   |  4     0     -1     -6    -9

    |         -4     4     -3      9

    |________________ I put that 0 in there because we are missing x^3

        4    -4     3     -9      0

The the other factor is 4x^3-4x^2+3x-9.

1 is obviously not going to make that 0.

Plug in -3 it gives you 4(-3)^3-4(-3)^2+3(-3)-9=-162 (not 0)

Plug in 3 gives you 4(-3)^3-4(-3)^2+3(-3)-9=72 (not 0)

Plug in 3/2 gives you 4(3/2)^2-4(3/2)^2+3(3/2)-9=0 so x=3/2 works as a solution.

Now let's find another factor

3/2  |     4       -4           3        -9

      |                6           3          9

      |________________________

            4          2           6        0

So we have 4x^2+2x+6=0.

The discriminant is b^2-4ac which in this case is (2)^2-4(4)(6). Simplifying this gives us (2)^2-4(4)(6)=4-16(6)=4-96=-92.  This is negative number which means the other 2 solutions are complex (not real).

So the other real solutions that satisfy the system is for x=3/2 or x=-1.

Since y=2x^2 then for x=3/2 we have y=2(3/2)^2=2(9/4)=9/2 and for x=-1 we have y=2(1)^2=2.

So we have the two real points (3/2 , 9/2)  and (-1,2)

Circle theorem:

The angle at the centre (T) is double the angle at the circumference (Q)

---> That also means that:

The angle at the circumference (Q) is half the angle at the centre (T)

Since T = 130 degrees;

Q = 130 divided by 2

   = 65°

___________________________________

Answer:

∠Q = 65°

Answer:

m<Q = 65°

Step-by-step explanation:

It is given that <T = 130°

To find the <Q

From the figure we can see that <T is the central angle made by the arc RS

And <Q is the angle made by the arc RS on minor arc.

We know that m<Q = (1/2)m<T

We have m<T = 130°

Therefore m<Q = 130/2 = 65°

Answer:

Step-by-step explanation:

(1) +(2) ⇒ (x -y -2z) +(-x +3y -z) = (4) +(8)

  2y -3z = 12

__

2(1) +(3) ⇒ 2(x -y -2z) +(-2x -y -4z) = 2(4) +(-1)

  -3y -8z = 7

___

The reduced system of equations is ...

Answer:

2y - 3z = 12.

-3y - 8z = 7.

Step-by-step explanation:

x - y - 2z = 4     (1)

-x + 3y - z = 8    (2)

-2x - y - 4z = -1   (3)

Adding (1) + (2):

2y - 3z = 12.

2 * (1) + (3) gives:

-3y - 8z = 7.