What is the sum of the two solutions of the equation $x^2-4x-45=0$ ?

$-45$

$-5$

$0$

$4$

$9$

Approach

Note, you can solve this by graphing it in the calculator and finding $x$-intercepts. Alternatively, factoring:

$$ x^2-4x-45=0 $$ $$ (x-9)(x+5)=0 $$ $$ x=9 \text{ and } x=-5 $$ $$ 9+(-5) = \boxed{4} $$