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What is the answer for the 4th equation in question 3) ?...

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jayson94 | Salutatorian

Posted August 8, 2013 at 10:30 PM via web

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What is the answer for the 4th equation in question 3) ?

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samhouston | Middle School Teacher | (Level 1) Associate Educator

Posted August 9, 2013 at 1:02 AM (Answer #1)

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x^4 -5x^2 - 36

First, imagine the trinomial as...
x^2 - 5x - 36
Factor this equation.

You need to find two numbers whose sum is -5 and product is -36.
-9 + 4 = -5
-9 * 4 = -36

x^2 - 5x - 36
(x - 9)(x + 4)

Now change x to x^2 to get the original trinomial.
(x^2 - 9)(x^2 + 4)

You can check your answer using FOIL.

(x^2 - 9)(x^2 + 4)
x^4 + 4x^2 - 9x^2 - 36
x^4 - 5x^2 - 36

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