Question

What is the equation in point-slope form of the line passing through (1, 9) and (−1, 11)?

y + 9 = −(x − 1)
y − 9 = 1(x + 1)
y + 9 = 1(x + 1)
y − 9 = −(x − 1)

Answer 1

Point slope form:

`y-y_1=m(x-x_1)`

m=slope
(x1,y1)

First we need to find the slope using the slope formula:

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

Given the two coordinates:
(1, 9) and (−1, 11)

Plug them into the slope formula:

`(11-9=2)/(-1-1=-2) =slope`
Simplify:

`(2)/(-2) =-1`

Now we know that:
m=-1 and the (x1,y1) would be (1, 9)

Now we simply plug in the info:

`y-9=-(x-1)`

Final answer: y − 9 = −(x − 1)