Question

For which values of x is the function y = 5 / (x-4)(x+5) not defined? Select all that apply.
A) -5
B) -4
C) 4
D) 5

Answer 1

$f(x)=\dfrac{5}{(x-4)(x+5)}\\\\(x-4)(x+5)\neq0\iff x-4\neq0\ and\ x+5=0\\\\x\neq4\ and\ x\neq-5\\\\Answer:\boxed{-5\ and\ 4}$