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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.2012-09-23

1 Answers 1

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

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?2012-09-23
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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.2012-09-23
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    Im sorry, didnt know that wasnt allowed D:2012-09-23
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    Yes @Mike , thanks. I've already fixed that.2012-09-23
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    Don't worry, @aayush: we all do those things at the beginning.2012-09-23