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If x+1 is a factor of $2x^3 + ax^2 + 2bx + 1$ then find the values of $a$ and $b$ given that $2a - 3b = 4$

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Please pick a descriptive question title, in the future. –  rschwieb Sep 23 '12 at 13:25

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up vote 6 down vote accepted

$$(x+1)\mid (2x^3+ax^2+2bx+1)\Longleftrightarrow 2(-1)^3+a(-1)^2+2b(-1)+1=0$$

So we get the following linear system in the unknowns $\,a,b\,$ :

$$\begin{align*}a-2b&=1\\2a-3b&=4\end{align*}$$

Can you take it from here?

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Thanks man..Can you help with the other one too? –  Aayush Agrawal Sep 23 '12 at 12:48
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You're kidnapping your own question and asking a new one after the original one! Don't ever do that again: it is not polite, it is very confusing and it is not correct for the same person to give two answers within the same thread. I'm going to erase the new question and you please ask it as a new* one. –  DonAntonio Sep 23 '12 at 12:53
    
Im sorry, didnt know that wasnt allowed D: –  Aayush Agrawal Sep 23 '12 at 14:02
    
Yes @Mike , thanks. I've already fixed that. –  DonAntonio Sep 23 '12 at 14:09
    
Don't worry, @aayush: we all do those things at the beginning. –  DonAntonio Sep 23 '12 at 14:10

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