Find the equation of the line that is perpendicular to the graph of y=1/2x + 9 and passes through (8,-5)

Question

anonymous · Answer

Hi --- I can help you with this.  First of all, can you tell me what the slope of your line is?
$$y = \frac 12x + 9$$

anonymous · Answer

slope is 1/2

anonymous · Answer

Good!  Now, can you tell me what the slope of a *perpendicular* line would be?

anonymous · Answer

would it be the reciprocal?

anonymous · Answer

Close.  The *negative reciprocal".  
For example, a line of slope  5  would have perpendicular slope  -1/5.
As a second example, a line of slope  -1/3  would have slope  3.
So ... what's the slope of your perpendicular line?

anonymous · Answer

You need to "flip" AND change the sign ...

anonymous · Answer

-2?

anonymous · Answer

Good!  So now, you want the line with slope  -2  that passes through the point (8,-5) .  (If you've heard of point-slope form, that would be great to use right now!  Or, you can certainly do it different ways...)

anonymous · Answer

I got y = -2x + 11

anonymous · Answer

That's what I got, too!  Awesome!

anonymous · Answer

Thank you!!! Really helped!

anonymous · Answer

You're welcome!  Have a great day...