Question

A line that includes the points (3, -5) and (0,r) has a slope of -3. What is the value of r?

Answer 1

r=4

Explanation:

What does slope mean? Slope is the amount of units that y moves when x increases by 1. So, in this case, the slope is -3 and therefore y moves -3 every time x increases by 1.

When x decreases by 3 in this case, then y would increase by 9 because the slope is -3. So if the y value increases by 9, add 9 to -5.

r=4

Answer 2

r = 4

Explanation:

calculate the slope m using the slope formula and equate to - 3

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

with (x₁, y₁ ) = (3, - 5 ) and (x₂, y₂ ) = (0, r )

m =
`(r-(-5))/(0-3)` =
`(r+5)/(-3)`

equating to - 3

`(r+5)/(-3)` = - 3 ( multiply both sides by - 3 to clear the fraction )

r + 5 = - 3 × - 3 = 9 ( subtract 5 from both sides )

r = 4