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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
avatar+106981 
+3

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
avatar+279 
+1

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)

 

smileysmileysmiley

CreatorRozen  Sep 24, 2019
edited by CreatorRozen  Sep 24, 2019
 #3
avatar+106981 
+1

That is good.  wink

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
 #4
avatar+2551 
+2

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

CalculatorUser  Sep 25, 2019
 #5
avatar+106981 
+2

That is fine. So long as the answer is correct we can all use whatever method we want.

Melody  Sep 25, 2019

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