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Help.

NotSoSmart  Jan 11, 2018
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x^4  + 5x^3  + 7x^2  - 3x - 10  = 0

 

If we  add the coefficients and constant term and get  0 then 1 is a root....so....

 

1 + 5 + 7  - 3  - 10   =    13  - 13   =    0

 

So 1  is a root

 

 

So.....we need to check  wheter 2  is a root...if not....then  -2 must be the other  rational root

 

So

 

(2)^4  + 5(4)^3 + 7(2)^2  - 3(2) - 10   >  0

 

So   -2  is the other rational root

 

So    -2, 1   are the rational roots

 

 

cool cool cool

CPhill  Jan 11, 2018

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