Factor completely.
x²-3x-28
a. (x - 7)(x+4)
b. (x + 7)(x-4)
c. (x + 14)(x-2)
d. (x + 14)(x + 2)

A. (x - 7)(x+4)

Step-by-step explanation:

To factor x²-3x-28, you need two numbers that add to get -3 and also multiply to get -28.

p + q = -3         At least one of p and q must be negative.

p * q = -28        

Find the factors of -28, then decide which two also add to get -3.

Trial and error:

-2 and 14 multiply to be -28. But when added, they are 12, not 3.

If you multiply 7 and -4, the product is -28. If you add them, the are 3, not -3.

Multiply -7 and 4, the product is -28. Added together, the sum is -3.

x² - 3x - 28  = (x + q) (x + p)

q = -7

p = 4

x² - 3x - 28 = (x - 7)(x + 4)

Check your work: Expand (x - 7)(x+4). Use FOIL (first, outside, inside, last) to multiply every term in one bracket by every term in the other bracket.

(x - 7)(x+4)        

= x² + 4x - 7x - 28         Combined like terms 4x and -7x

= x² - 3x - 28          Same as question, so the answer is correct.

something over 10 so ? /10

step-by-step explanation: