Question

A student was asked to find the slope of the line through the points (4,8) and (-3,5). His answer,
`-(3)/(7)`, was incorrect. He showed his work as
`(5-8)/(4-(-3))`=
`-(3)/(7)`=
`-(3)/(7)`.

What went wrong? Give the correct slope.

Answer 1

`m=(-3)/(-7)`

Explanation:

Given the following question:

Point A = (4, 8) = (x1, y1)
Point B = (-3, 5) = (x2, y2)

In order to find the slope any two points given we use the formula to find slope or rise/run.


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

`m=(5-8)/(-3-4) =(-3)/(-7)`

`m=(-3)/(-7)`

The reason why the students answer is incorrect because he substituted incorrectly. More specifically the run part of the formula for slope. The formula for slope goes x2 - x1 which means it should be -3 - 4, not -4 - 3, which will give you the answer -7.

Hope this helps.