Question

Write an equation of the line that passes through the pair of points (5, 8) and (9, 16).

Answer 1

Answer:  Choice D)  y = 2x-2

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Explanation:

Apply the slope formula

m = (y2-y1)/(x2-x1)

m = (16-8)/(9-5)

m = 8/4

m = 2

Then use this slope, along with another point such as (x,y) = (5,8) to find b

y = mx+b

8 = 2*5+b

8 = 10+b

8-10 = b

-2 = b

b = -2

Or you could use the other point (x,y) = (9,16)

y = mx+b

16 = 2*9+b

16 = 18+b

16-18 = b

-2 = b

b = -2

Either way, we get the same y intercept.

So because m = 2 is the slope and b = -2 is the y intercept, we go from y = mx+b to y = 2x-2

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To help verify the answer, note how plugging x = 5 leads us to...

y = 2x-2

y = 2*5 - 2

y = 10-2

y = 8

So x = 5 and y = 8 pair up together. This verifies (5,8) is on the line.

Through similar steps, you should find that the input x = 9 leads to the output y = 16. So that would confirm (9,16) is also on the line, and fully confirm the answer.

Answer 2

Answer:

D: y = 2x - 2

Step-by-step explanation:

1. $\frac{16-8}{9-5}$ = 2

2. y = 2x + b

3. Insert the points into the equation: 8 = 10 + b

4. b = -2

5. y = 2x - 2