Explanation:
1. x(x+2) = 0
It is either x = 0, or x+2 = 0, so we simplify to x=0, -2
2. (7x+2)(5x-4)=0
Same thing, 7x+2=0 and 5x-4=0, so x = -2/7 or 4/5
3. x^2-14x+45=0
Now we have something different, so we have to factor this to:
(x-9)=0 and (x-5)=0, and now we can simplify this to x=9,5
4. x^2+13x=-42
We can't factor this yet until one side is equal to 0, so we move "-42" to the other side to form x^2+13x+42.
We factor this to get (x+6)=0, and (x+7)=0, so x=-6,-7