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My algebra is very rusty, it's been about 15years since I studied, and I was stumped recently when trying to rearrange this formula;

$$a = b^2 + 2b^2(1 - b)$$

to give $b$ in terms of $a$.

Can someone show me step by step working please :)

I remember 'change side, change sign' but it all gets very confusing very quickly.

Thanks!


So,

$$2b^2(1-b)\Rightarrow 2b^2 - 2b^3$$

Giving

$$a = b^2 + 2b^2 - 2b^3$$

$$a = 3b^2 - 2b^3$$

$$a + 2b^3 - 3b^2 = 0$$

is this right so far?

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    That's completely correct.2012-05-16
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    Well now I'm stuck how to get b = ...2012-05-16
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    You were stumped, not because you are rusty, but because you probably never learned how to solve third degree equations - this topic is not in the syllabus of the educational systems with which I am familiar.2012-05-16
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    Quite right Gerry, I foolishly assumed that because it only had a's and b's it must be very simple, haha. That' me reminded then :)2012-05-17

4 Answers 4