Rhys_M
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For part b below, I plugged 1/8 into root[(1-5x)/(1+x)] which gave root3/3

So i then plugged 1/8 into my estimation expansion of 1-4x-3x²/2 , and multiplied the result by 3
(As you x3 to go from root3/3 to root3), giving 231/128.
However the MS says the answer's 128/77 - what have i done wrong? Thanks

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FlatearthFTW
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What would you get if, instead of multiplying by 3 on both sides, you invert the fractions on both sides?
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Rhys_M
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(Original post by FlatearthFTW)
What would you get if, instead of multiplying by 3 on both sides, you invert the fractions on both sides?
Then it'd be 3/root3 and 1/root3.
How does that help?
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ghostwalker
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(Original post by Rhys_M)
Then it'd be 3/root3 and 1/root3.
How does that help?
Substituting x=1/8 will give you

\sqrt{\dfrac{1}{3}} = \dfrac{p}{q} for some p,q that you've determined.

Now follow FlatearthWTF's suggestion.
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username1732133
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(Original post by Rhys_M)
Then it'd be 3/root3 and 1/root3.
How does that help?
Two ways of looking at it.

\frac{1}{\sqrt{3}}=\frac{77}{128} or \frac{\sqrt{3}}{3}=\frac{77}{128}

Leading to two possible answers.
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Rhys_M
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(Original post by Plücker)
Two ways of looking at it.

\frac{1}{\sqrt{3}}=\frac{77}{128} or \frac{\sqrt{3}}{3}=\frac{77}{128}

Leading to two possible answers.
(Original post by ghostwalker)
Substituting x=1/8 will give you

\sqrt{\dfrac{1}{3}} = \dfrac{p}{q} for some p,q that you've determined.

Now follow FlatearthWTF's suggestion.
(Original post by Rhys_M)
Then it'd be 3/root3 and 1/root3.
How does that help?
Thanks so much everyone
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