Explanation:
6x² - 6x - 72 = 0
Using. Completing the squares method.
6x²/6 - 6x/6 = 72/6
x² - x = 12
Take the coefficient of x, halve and square and add to both sides.
(1/2)² = 1/4
( x + 1/4)² = 12 + 1/4
(x + 1/4)² = 48 + 1 /4
(x + 1/4)² = 49/4
x + 1/2 = 7/2
x = 7/2 ±1/2
x = 4 or x = 3