Question

If f (x) = x^2 -2x -11, then which of the following values of x solves f(x)=4?

Answer 1

Answer:

$\huge\boxed{x=-3\ \vee\ x=5}$

Step-by-step explanation:

$f(x)=x^2-2x-11\\\\f(x)=4\\\\x^2-2x-11=4\qquad|\text{subtract 4 from both sides}\\\\x^2-2x-15=0\\\\x^2+3x-5x-15=0\\\\x(x+3)-5(x+3)=0\\\\(x+3)(x-5)=0\iff x+3=0\ \vee\ x-5=0\\\\\boxed{x=-3\ \vee\ x=5}$