Question

The points (-4, 1) and (r. -7) lie on a line with slope - 1. Find the missing coordinate r.

Answer 1

r = 4

Explanation:

You need to use the slope formula to solve for r.

1. Write out the equation using slope formula

(-7 - 1)/(r + 4) = -1

2. Multiply both sides by r + 4

-8 = -r - 4

3. Add 4 on both sides. Optionally, use the reflexive property of equality.

-r = -4

4. Multiply both sides by -1

r = 4

Answer 2

r = 4

Explanation:

Using the point-slope form of the equation for a line, the line with slope -1 through point (-4, 1) is ...

y -1 = -1(x +4)

Substituting the second point, we have an equation for r:

-7 -1 = -1(r +4)

8 = r +4 . . . . . . . divide by -1

r = 4 . . . . . . . . subtract 4

The missing coordinate is 4. The second point is (4, -7).