You can put this solution on YOUR website! This equation is in the form 0=ax^2+bx+c where a=1,b=4,and c=-21.
Combine all terms without variable on one side by subtracting both sides by 25.
x^2+4x-21=0
Then, factor this equation.
(x+7)(x-3)=0
The equation is now in the form 0=(x-p)(x-q), where x-p=0 and x-q=0.
So, x=-7 and +3