How do you factor y=x^2 - 2x - 15y=x2−2x−15 ?

2 Answers
Jim G.
May 28, 2018

y=(x-5)(x+3)y=(x−5)(x+3)

Explanation:

"the factors of - 15 which sum to - 2 are - 5 and + 3"the factors of - 15 which sum to - 2 are - 5 and + 3

y=(x-5)(x+3)y=(x−5)(x+3)

Geoffrey T
May 28, 2018

(x-5)(x+3)(x−5)(x+3)

Explanation:

First, find two numbers that have a sum of -2 (the second term) and have a product of -15 (the third term)
Multiples of 15:
1 | 15
3 | 5
-5 * 3 = -15−5⋅3=−15 and -5 + 3 = -2−5+3=−2
Use this to "split the middle" of the polynomial
x^2 - 5x + 3x - 15x2−5x+3x−15
Factor
x(x-5) + 3(x-5)x(x−5)+3(x−5)
(x-5)(x+3)(x−5)(x+3)

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