## Precalculus (6th Edition) Blitzer

$\left\{0, 4\right\}$
Subtract $20x$ on both sides of the equation to obtain: $5x^2-20x=0$ Factor out $5x$ to obtain: $5x(x-4)=0$ Equate each factor to zero then solve each equation to obtain: $5x=0 \text{ or } x-4=0 \\x=\frac{0}{5} \text{ or } x-4=0 \\x=0 \text{ or } x=4$ Thus, the solution set of the given equation is $\left\{0, 4\right\}$.