+0  
 
+1
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avatar+634 

Factor this expression.

\(-2x^2+x+21=0\)

AdamTaurus  Sep 13, 2017

Best Answer 

 #1
avatar+5256 
+3

Hey! This is the same equation that you get from the last question.

 

You can solve it by factoring like this....

 

-2x2 + x + 21  =  0

 

Multiply the  -2  and  21  to get  -42  .

Now split the middle term with two numbers that add to  1  and multiply to  -42 .

 

-2x2 - 6x + 7x + 21  =  0

                                             Factor a  -2x  out of the first two terms and a  7  out of the last two terms.

-2x(x + 3) + 7(x + 3)  =  0

                                             Factor  a  (x + 3)  out of both remaining terms.

(x + 3)(-2x + 7)  =  0

hectictar  Sep 13, 2017
Sort: 

3+0 Answers

 #1
avatar+5256 
+3
Best Answer

Hey! This is the same equation that you get from the last question.

 

You can solve it by factoring like this....

 

-2x2 + x + 21  =  0

 

Multiply the  -2  and  21  to get  -42  .

Now split the middle term with two numbers that add to  1  and multiply to  -42 .

 

-2x2 - 6x + 7x + 21  =  0

                                             Factor a  -2x  out of the first two terms and a  7  out of the last two terms.

-2x(x + 3) + 7(x + 3)  =  0

                                             Factor  a  (x + 3)  out of both remaining terms.

(x + 3)(-2x + 7)  =  0

hectictar  Sep 13, 2017
 #2
avatar+634 
+1

The other guy's answer really confused me because he didn't know how to use Latex, so I worked most of it out as best I could then asked this.

AdamTaurus  Sep 13, 2017
 #3
avatar+91051 
0

Thanks Hectictar,

Adam, I hope that you said 'thank you' to both of your answerers!

So far I have not seen even one though   sad

Melody  Sep 13, 2017

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