Question

What is an equation for the line parallel to y = -3x – 5 that contains (-1, 8)?

Answer 1

Answer: y = -3x+5

slope = -3

y intercept = 5

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Explanation:

The given line is in the form y = mx+b, so the slope is m = -3

Any parallel line to this one will also have the same slope, but a different y intercept.

Plug (x,y) = (-1,8) and m = -3 into y = mx+b so we can find new y intercept.

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y = mx+b

8 = -3(-1) + b

8 = 3+b

8-3 = b

5 = b

b = 5

So because m = -3 and b = 5, this means we have y = -3x+5 as our answer.

Answer 2

Answer: y = -3x + 5

Explanation:

For a line to be parallel the slope needs to be the same.

And we are given a point to work with:

So let’s use point-slope form:

We know that the slope is -3
And the point is (-1,8)

And the form:
y - y1 = m(x - x1)
y - 8 = -3(x -(-1))
y - 8 = -3(x + 1)
y - 8 = -3x - 3
y = -3x - 3 + 8
y = -3x + 5

Therefore, our equation is y = -3x + 5