In the expansion of `(1+x)^n`, Then sum of the coefficients of odd power of x is

Explanation

expansion of `(1+x)^70 = sum_(r=0)^n .^nC_r(x)^r`

`= .^nC_1 + .^nC_3 + .^nC_5 + ......`

when `x=1`

`(2)^70 = .^nC_0 + .^nC_1 + .^nC_2 + ........+ .^nC_n` let 2A

when `x=-1`

`0 = .^nC_0 - .^nC_1 + .^nC_2- .^nC_3 .....`

`= (.^nC_0 + .^nC_2 + .^nC_4 + ....) - (.^nC_1 - .^nC_3 .....)`

so `.^nC_0 + .^nC_2 + .^nC_4 ..... = .^nC_1 + .^nC_3 + .^nC_5 ......`

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