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    Hey. I really need some help. Got a tip off that this question was in tomorrows test :rolleyes:

    Use 2(1+x/8)^1/3 = 2 + x/12 - x²/288, to work out ³√15

    Thanks everyone!
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    rewrite 2(1 + x/8)^1/3 as (8 + x)^1/3, let x = 7, and bingo it give you the cube root of 15
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    (Original post by rpotter)
    rewrite 2(1 + x/8)^1/3 as (8 + x)^1/3, let x = 7, and bingo it give you the cube root of 15
    What if it is non calculator? I think they give you the expansion for a reason?
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    well then express it as fractions, although its not an exact answer just an approximation
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    (Original post by rpotter)
    well then express it as fractions, although its not an exact answer just an approximation
    ??... don't quite understand how you go about that. Can you explain it please. Do you mean put x as 13/2?
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    Just set x=7 in your expansion.
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    (Original post by dvs)
    Just set x=7 in your expansion.
    ahhhh.. ok thanks
 
 
 
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