For what real values of $a$ is the expression $\frac{a+3}{a^2-4}$ undefined? List your answers in increasing order separated by commas.
The only way for a number to be undefined (well, not only, but in this case) is if the denominator is 0. So that is what we do: set the denominator to 0.
a^2 - 4 = 0
a^2 = 4
a = -2, 2
Simple!
:)
+126 
