Question

B (7,-3)

C (6,-),
A (4,-9)
What is the y-coordinate of point C?
OA A
OB. -5
Oc. -6
OD. -7

Answer 1

`y = -5`

Explanation:

Given

`B = (7,-3)`

`C = (6,y)`

`A = (4,-9)`

Required

The y coordinate of C

Since A, B and C are on the same line, the slope of AB and the slope of AC will be the same.

Slope (m) is calculated as:

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

For AC

`A = (4,-9)`
`C = (6,y)`

`m = (y - -9)/(6 - 4)`

`m = (y +9)/(2)`

For AB

`A = (4,-9)`
`B = (7,-3)`

`m = (-3 --9)/(7-4)`

`m = (-3 +9)/(3)`

`m = (6)/(3)`

`m = 2`

So, we have:

`m = (y +9)/(2)` and
`m = 2`

`m = m`

`(y +9)/(2) = 2`

Multiply both sides by 2

`y +9 = 4`

Solve for y

`y = 4-9`

`y = -5`

Hence, the y coordinate of C is -5