So Rina breathed out. She looked at x² + 5x + 6 again. She drew her two parentheses: ( _ + _ )( _ + _ ).

Then the magic trick: if the product is zero, one of the factors must be zero.

Problem 8: x² - 4x - 12 = 0 . Multiply to -12, add to -4? -6 and +2. (x - 6)(x + 2) = 0 → x = 6, x = -2.

What two numbers multiply to 6 and add to 5? 2 and 3.