The equation in undefined when the denominator is equal to 0.
The denominator is (x+5) (x+11)
Solve for the x's to make the equations equal 0:
x+5 = 0
Subtract 5 from each side:
x =-5
x+11 = 0
Subtract 11 from each side:
X = -11
There are two answers -5 and -11.