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# Factoring Trinomials - #whoskeepingcount

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Factor the trinomial below. Write each factor as a polynomial in descending order.

8x^2 - 10x - 25

Sep 24, 2019

#1
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8x^2 - 10x - 25

8*-25=-200

So I want 2 numbers that add to -10 and multiply to -200

The bigger one will be negative and the smaller one will be positive (absolute values I mean)

The fairly obvious combination is   -20 and 10

-10x is replaced with -20x+10x

= 8x^2 -20x+10x - 25

Now factorise in pairs

= 4x(2x-5) + 5(2x-5)

= (4x+5)(2x-5)

Sep 24, 2019
#2
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Thank you Melody, I think i understand it better now

(you might have just taught me something i would have never thought about using or doing)

CreatorRozen  Sep 24, 2019
edited by CreatorRozen  Sep 24, 2019
#3
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That is good.

It is a good way to do these but a lot of teachers teach what I think is a more complicated method.

Melody  Sep 24, 2019
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My teacher taught in the same way as you did, Melody. But I personally use the Table Method

CalculatorUser  Sep 25, 2019
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That is fine. So long as the answer is correct we can all use whatever method we want.

Melody  Sep 25, 2019