Question

A student finds the slope of the line between (8, 17) and (1, 4). She write 17-4/1-8. What mistake did she make?

A) She mixed up the x- and y-values.
B) She should have added the values, not subtracted them.
C) She used y-values where she should have used x-values.
D) She did not keep the order of the points the same in the numerator and the denominator.

Answer 1

Answer: OPTION D.

Explanation:

The formula that is used to calculate the slope of a line is:

`m=(y_2-y_1)/(x_2-x_1)`

Where
`(x_1,y_1)` and
`(x_2,y_2)` are two points on the line.

In this case the student finds the slope of the line that passes trough these points:

`(8, 17)\\(1, 4)`

You can notice that she writes in the numerator that:

`y_2=17\\y_1=4`

So she chose the point
`(1, 4)` as
`(x_1,y_1)` and the point
`(8, 17)` as
`(x_2,y_2)`.

Then
`x_2` and
`x_1` in the denominator must be:

`x_2=8\\x_1=1`

Therefore, she did not keep the order of the points the same in the numerator and the denominator.