Answer
The solutions are $x=8$ and $x=-5$.
Work Step by Step
The given equation is
$\Rightarrow x^2-3x-40=0$
The equation is easily factorable. So, solve by factoring.
$\Rightarrow x^2-3x-40=0$
Rewrite $-3x$ as $-8x+5x$.
$\Rightarrow x^2-8x+5x-40=0$
Group the terms.
$\Rightarrow (x^2-8x)+(5x-40)=0$
Factor each group.
$\Rightarrow x(x-8)+5(x-8)=0$
Factor out $(x-8)$.
$\Rightarrow (x-8)(x+5)=0$
Use zero-product property.
$\Rightarrow x-8=0$ or $x+5=0$
Solve for $x$.
$\Rightarrow x=8$ or $x=-5$
Hence, the solutions are $x=8$ and $x=-5$.