Question

Find y if the slope between ( 4 , y ) and ( − 4 , 13 ) is − 1 .

Answer 1

y = 5

Explanation:

Use the formula for slope, which is represent by the variable "m".

`m = (y_(2)-y_(1))/(x_(2)-x_(1))`

The information in the formula is m = -1, point 1 (4, y) and point 2 (-4, 13).

The x and y values are from each point:

Point 1 (4, y) x₁ = 4 y₁ = y

Point 2 (-4, 13) x₂ = -4 y₂ = 13

Substitute (replace the variables with) the information into the formula.

`m = (y_(2)-y_(1))/(x_(2)-x_(1))`

`-1 = (13-y)/(-4-4)` Simplify.

`-1 = (13-y)/(-8)`

Since we want to find "y", we are going to isolate it (separate it from the other numbers). We do this by cancelling out the information on the side with "y". Numbers cancel out when there are reverse operations on them. (For example, if you have positive 8, subtracting 8 will cancel it out).

`-1=(13-y)/(-8)` Multiply by sides by -8. It cancels out on the right.

`-1*-8=13-y` Multiply -1*-8

`8=13-y` Subtract 13 on both sides. It cancels out on the right.

`8-13=-y` Subtract 8-13

`-5=-y` Divide both sides by -1

`y=5` Answer for y