Brie's question from Facebook (finding equation of perpendicular line)

Jameson

Staff member
Brie writes:
Hi everyone! I need a little help with finding a perpendicular line using an ordered pair and the equation to the previous line.

The equation is y= 3x+3 and the ordered pair is (1,1).

So far, I've used the slope-point equation to come up with such:

y-y1=m(x-x1)
y-1= -1/3(x-1)
y=(-1/3)(x)-(-1/3)(1)+1
At the end I ended up getting:
y=(-1/3)x+(1/3)+1
y=(-1/3)x+(4/3)

When I graph it, it's not going through the point (1,1) which it should. What am I doing wrong?

Thank you!

Last edited:

Jameson

You have solved the problem correctly actually! When you plug-in x=1 to your final equation you get $$\displaystyle y=-\frac{1}{3}(1)+\frac{4}{3}=\frac{4}{3}-\frac{1}{3}=\frac{3}{3}=1$$, so $y=1$ like we want it to.