Answer:
(x + 5) • (x + 3) • (x - 2) • (x - 4)
Explanation:
Step-1 : Multiply the coefficient of the first term by the constant 1 • 15 = 15
Step-2 : Find two factors of 15 whose sum equals the coefficient of the middle term, which is 8 .
-15 + -1 = -16
-5 + -3 = -8
-3 + -5 = -8
-1 + -15 = -16
1 + 15 = 16
3 + 5 = 8 That's it
Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above, 3 and 5
x2 + 3x + 5x + 15
Step-4 : Add up the first 2 terms, pulling out like factors :
x • (x+3)
Add up the last 2 terms, pulling out common factors :
5 • (x+3)
Step-5 : Add up the four terms of step 4 :
(x+5) • (x+3)
Which is the desired factorization
(x + 5) • (x + 3) • (x - 2) • (x - 4)