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If `(1 +x+x^2)^25 = a_0 + a_1x+ a_2x^2 +..... + a_50.x^50` then `a_0 + a_2 + a_4 + ... + a_50` is :A. evenB. odd and of the form `3n`C. odd and of the form `(3n-1)`D. odd and of the form `(3n+1)` |
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Answer» Correct Answer - A `(a)` Putting `x=1` and `-1` and adding `a_(0)+a_(2)+…+a_(50)=(3^(25)+1)/(2)` `=((1+2)^(25)+1)/(2)` `=("^(25)C_(0)+^(25)C_(1)*2+^(25)C_(2)*2^(2)+^(25)C_(25)*2^(25)+1)/(2)` `=(2[1+^(25)C_(1)+^(25)C_(2)*2+...+^(25)C_(25)*2^(24)])/(2)` `=2[13+^(25)C_(2)+...+^(25)C_(25)*2^(23)]` |
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