Answer:
(x-3) (x-7)
Step-by-step explanation:
The first term is, x2 its coefficient is 1 .
The middle term is, -10x its coefficient is -10 .
The last term, "the constant", is +21
Step-1 : Multiply the coefficient of the first term by the constant 1 • 21 = 21
Step-2 : Find two factors of 21 whose sum equals the coefficient of the middle term, which is -10 .
-21 + -1 = -22
-7 + -3 = -10 That's it
Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above, -7 and -3
x2 - 7x - 3x - 21
Step-4 : Add up the first 2 terms, pulling out like factors :
x • (x-7)
Add up the last 2 terms, pulling out common factors :
3 • (x-7)
Step-5 : Add up the four terms of step 4 :
(x-3) • (x-7)
Which is the desired factorization