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If the coefficients of ar−1, ar and ar+1 in the binomial expansion (1+a)n are in the arithmetic progression, prove that n2−n(4r+1)+4r2−2=0 Or The 2nd, 3rd and 4th terms in the expansion of (x+y)n are 240, 720 and 1080, respectively. Find the values of x, y and n. |
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Answer» If the coefficients of ar−1, ar and ar+1 in the binomial expansion (1+a)n are in the arithmetic progression, prove that n2−n(4r+1)+4r2−2=0 Or The 2nd, 3rd and 4th terms in the expansion of (x+y)n are 240, 720 and 1080, respectively. Find the values of x, y and n. |
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