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    (a+b)^n and (1+x)^n..whats the difference?
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    (Original post by ShOcKzZ)
    (a+b)^n and (1+x)^n..whats the difference?
    The binomial expansion only works for (1+x)^n so you have to take out a factor of a^n from the first if you're going to use the normal expansion
    (a+b)^n = a^n(1+b/a)^n
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    (Original post by Bezza)
    The binomial expansion only works for (1+x)^n so you have to take out a factor of a^n from the first if you're going to use the normal expansion
    (a+b)^n = a^n(1+b/a)^n
    You can still use the nCr thing for (a + b)^n though.

    (a + b)^n = a^n + (nC1)a^(n - 1)b^1 + (nC2)a^(n - 2)b^2 + ... + b^n
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    (Original post by Nylex)
    You can still use the nCr thing for (a + b)^n, yeah?

    (a + b)^n = a^n + (nC1)a^(n - 1)b^1 + (nC2)a^(n - 2)b^2 + ... + b^n
    Yeah, but in the a-level formula book they give you the expansion for (1+x)^n so it's easiest just to rearrange and use it (in my opinion)
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    (Original post by Bezza)
    The binomial expansion only works for (1+x)^n so you have to take out a factor of a^n from the first if you're going to use the normal expansion
    (a+b)^n = a^n(1+b/a)^n
    i c

    so would (2 + 3x)^5 = 2^5.(1 + 1.5x)^5 ?
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    (Original post by ShOcKzZ)
    i c

    so would (2 + 3x)^5 = 2^5.(1 + 1.5x)^5 ?
    Yep
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    (Original post by Bezza)
    Yep
    thanks.
 
 
 
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