How do you factor #x^2-2x-15=0# ?

1 Answer
EZ as pi
Sep 17, 2016

#(x-5)(x+3)#

Explanation:

#x^2 -2x-15=0#

Find factors of 15 which SUBTRACT (because of MINUS 15) to give 2.

#rarr#The factor pairs of 15 are: #1xx15 and 3xx5#

#rarr 5-3 = 2" "rarr# so 5 and 3 are the factors we need.

The signs in the brackets will be DIFFERENT (because of MINUS 15)
- there must be more negatives, because of MINUS 2.
#rarr# the bigger factor will be negative

#(x-5)(x+3)#

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