Question

Find the equation of the line that is perpendicular to y = x+1
and contains the point (9,12).

Answer 1

y = -x + 21

Explanation:

Equations that are perpendicular don't normally have the same slope as the original equation..

When you graph the given equation and the point, we can see that in order to make an equation that would cross through (9,12) and the line, we would need an equation with a negative slope.

**Using desmos (online graphing calculator)

If we continue to plug in numbers for our slope, we see that the equation

y = -x + 21 goes through point (9,12) and is perpendicular (intersecting or crossing through) line y = x + 1.

We can check our work by plugging in the coordinates of the point 9, 12 into our equations to see if they equal the same values..

y = -x + 21 --> 12 = -9 + 21 --> 12 = 21 - 9 --> 12 = 12 (correct)