Question

7x to the third power - 7x to the second power =?

Answer 1

7x³-7x²
You have to divide each by the greatest common factor. In this case that is 7x²
So now you have 7x²(x+1). Now you set each factor to 0
x+1=0
x=-1
and 
7x²=0
x=0
Your answers are x=-1 and x=0