How do you factor the expression #x^2 - 13x + 40#?

1 Answer
Dec 12, 2015

Answer:

#(x-5)(x-8)#

Explanation:

There are many ways to factor. One method I like to use is the diamond method when you try to find the two numbers that add up to b and multiply to ac.
#y=ax^2+bx+c#

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So you want to find two numbers that add up to -13 and multiply to 40. You can find the factors of 40 and find the pair that adds up to -13. -8 and -5 multiply to 40 and add up to -13.

#(x-5)(x-8)=x^2-13x+40#

You can use foil to test it

#x^2+(-8x)+(-5x)+40=x^2-13x+40#

#x^2-13x+40=x^2-13x+40#