What are the holes of the function f(x) = (x^2 + 3x - 4)/(x^2 + 9x + 20)?
That will be where the numerator and denominator are both zero.
x^2+3x-4 = (x+4)(x-1)
x^2+9x+20 = (x+4)(x+5)
so, ...
x^2+3x-4 = (x+4)(x-1)
x^2+9x+20 = (x+4)(x+5)
so, ...