Final: Arrange First

The zero product rule only works when a product equals zero. If the equation has a number on the right side, first move every term to the left side so that the right side is zero. Then factor the left side and set each factor equal to zero.

For example, x^2 + 2x = 24 becomes x^2 + 2x - 24 = 0 after you subtract 24 from both sides. The left side factors as (x + 6)(x - 4), so x = -6 or x = 4. Read the signs of the rearranged equation, not the original one, because moving the 24 changed the constant.