finding slope

Question

Find y if the line through (5, 4) and (9, y) has a slope of 3.

y= ?

Answer 1

YOU KNOW THE FORMULA for slope; substitute 3 for m and substitute all of the other givens from the two points.

You will then have an equation with many numbers in it, and just the unknown letter y.

 

Now solve for y, using Algebra skills.

Answer 2

Since you mentioned "graphs" and "graphs of functions," you should use the fact that:

     slope = rise over run

 

The "run" from point (5,4) to (9,y) is 4   (that is, 9-5).

The slope is 3.

The "rise" is 3*4=12.  That means that (y-4)=12.    y=16.