We are given the quadratic equation

.
Note that if x=0, both sides of the equation are equal to 0.
So x=0 is a solution.
For

, then we can divide both sides of the equation by x, and we get x=-5.
Thus, the solution set is {0, -5}.
Remark: another way to solve the equation is to take -5x to the left hand side:

,
then we factorize x as

.
Thus we see that x is either 0, or -5.