Step-1 : Multiply the coefficient of the first term by the constant 1 • -12 = -12
Step-2 : Find two factors of -12 whose sum equals the coefficient of the middle term, which is -1 .
-12 + 1 = -11
-6 + 2 = -4
-4 + 3 = -1 That's it
Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above, -4 and 3
a2 - 4a + 3a - 12
Step-4 : Add up the first 2 terms, pulling out like factors :
a • (a-4)
Add up the last 2 terms, pulling out common factors :
3 • (a-4)
Step-5 : Add up the four terms of step 4 :
(a+3) • (a-4)
Which is the desired factorization
Answer: (a+3) • (a-4)
