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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)`

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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