Expert: Lynn Houston - 5/13/2010

Question
So my teacher said to find the y- intercept you had to use x=0 and to find the x-intercept you had to use y=0. Do you know how to explain this. Im not sure where she wants us to put the 0's.

Answer
whatever equation you have, you fill in 0 for x to find the y intercept and then fill in 0 for y to find the x intercept.  

Let's say  y = 2x + 4  to find the y intercept, substitute zero for x and solve for y.  so
y = 2(0) + 4 or
y = 4

To find the x intercept, substitute zero for y and solve for x.  so

0 = 2x + 4  subtract 4 from both sides
-4 = 2x    divide both sides by 2
-2 = x

make sense?