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how do i factor out 6x^2-x-1?

 Oct 29, 2015

Best Answer 

 #1
avatar+6045 
+10

Since the constant term is -1 you know your factors are going to be

 

\(6x^2 -x -1 = (a x + 1)(b x -1) = (ab)x^2+(b-a)x-1\)

 

\(a b =6, (b-a)=-1 \\ b=a-1 \\ a(a-1) = 6 \\ a=3, b=2\)

 

\(6x^2-x-1 = (3x+1)(2x-1)\)

.
 Oct 29, 2015
 #1
avatar+6045 
+10
Best Answer

Since the constant term is -1 you know your factors are going to be

 

\(6x^2 -x -1 = (a x + 1)(b x -1) = (ab)x^2+(b-a)x-1\)

 

\(a b =6, (b-a)=-1 \\ b=a-1 \\ a(a-1) = 6 \\ a=3, b=2\)

 

\(6x^2-x-1 = (3x+1)(2x-1)\)

Rom Oct 29, 2015
 #2
avatar+105509 
0

 

Thansk Rom    smiley

I would not have done it like that but I like that logic.

To use Chris's expression,  "I will put that in my tool belt"

I think that is what chris says anyway LOL

 Oct 29, 2015

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