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Binomial expansion a-level maths homework Watch

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    The first 3 terms in the expansion of (1+ax)^n are 1+21x+189x^2. Find the values of a and n.
    Please help!!
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    (Original post by Emmaturner45)
    The first 3 terms in the expansion of (1+ax)^n are 1+21x+189x^2. Find the values of a and n.
    Please help!!
    Expand (1+ax)^n using the binomial expansion, then compare coefficients of x and x^2.
    You should end up with two equations involving a and n.
 
 
 
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