Answer:
3x² - 12x - 36
= 3(x - 6)(x + 2)
Explanation:
3x² - 12x - 36 Find any common factor. All terms are divisible by 3.
= 3(x² - 4x - 12) Find two numbers that sum to -4 and whose product is -12. Replace -4 with these two numbers.
= 3(x² - 6x + 2x - 12) Group the terms splitting from the middle
= 3( (x² - 6x) + (2x - 12) ) Find the common factor in each group.
= 3( x(x - 6) + 2(x - 6) ) The groups have a common factor (x - 6).
= 3( (x - 6)(x + 2) ) Remove the extra brackets
= 3(x - 6)(x + 2) Fully factored