Q53 / 90 · JEE Main 2022 (25 Jun Shift 2) · Mathematics

If the sum of the co-efficients of all the positive even powers of x in the binomial expansion of 2x3+3x10 is 510-β·39, then β is equal to _____.

Correct answer: 83

Solution

Given,

Binomial expression 2x3+3x10, so its nth term is given by,

Tr+1=Cr102x310-r3xr

=Cr10210-r3rx30-4r

Now putting r=0,1,2,.....7 and adding all term we get 

2x3+3x10=C01021030x30+C1102931x26..............C7102337x2+C81022381x2....

2x3+3x10-C81022381x2.......=C01021030x30+C1102931x26..............C7102337x2

Put x=1 both side we get,

510-3960+20+3=C01021030+C1102931..............C7102337

510-3983=sum of even coefficients

So β=83

Hence, the correct answer is 83.

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