Question

How do you find the slope of the line that is (a) parallel and (b) perpendicular to the line through the pair of points: (-5, -10) and (0, 0)?

Answer 1

The slope of a straight line through `(x_1,y_1)= (-5,-10)` and `(x_2,y_2)=(0,0)` is given by

`m = (Delta y)/(Delta x) = (y_2-y_1)/(x_2-x_1)`

`= (0-(-10))/(0-(-5))`

`=2`

All parallel straight lines share the same slope.
so the slope of a line parallel to a line through `(-5,-10)` and `(0,0)` is `m=2`

The slope of a line perpendicular to a line with slope `m` is
`-1/m`
or, in this case,
`-1/2`