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JEE Main 202225 JuneEvening Shift
Exam
JEE Main
Year
2022
Date
25 June
Shift
Evening Shift
Subject
Mathematics
Chapter
Binomial Theorem

JEE Main 2022 · 25 June · Evening Shift · Mathematics · Binomial Theorem

If the sum of the co-efficients of all the positive even powers of...

If the sum of the co-efficients of all the positive even powers of xx in the binomial expansion of (2x3+3x)10is{\left(2{x}^{3} + \dfrac{3}{x}\right)}^{10} is{5}^{10} - \beta \cdot {3}^{9},then, then\beta is equal to _____.

Correct answer

0

Step-by-step solution

Given,

Binomial expression (2x3+3x)10{\left(2{x}^{3} + \dfrac{3}{x}\right)}^{10}, so its nth{n}^{th} term is given by,

Tr+1=Cr10(2x3)10−r(3x)r{T}_{r + 1} = Cr 10 {\left(2{x}^{3}\right)}^{10 - r}{\left(\dfrac{3}{x}\right)}^{r}

=Cr10210−r3rx30−4r= Cr 10 {2}^{10 - r}{3}^{r}{x}^{30 - 4r}

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

(2x3+3x)10=C01021030x30+C1102931x26..............C7102337x2+C81022381x2....{\left(2{x}^{3} + \dfrac{3}{x}\right)}^{10} = C0 10 {2}^{10}{3}^{0}{x}^{30} + C1 10 {2}^{9}{3}^{1}{x}^{26} . . . . . . . . . . . . . . C7 10 {2}^{3}{3}^{7}{x}^{2} + C8 10 {2}^{2}{3}^{8}\dfrac{1}{{x}^{2}} . . . .

(2x3+3x)10−C81022381x2.......=C01021030x30+C1102931x26..............C7102337x2{\left(2{x}^{3} + \dfrac{3}{x}\right)}^{10} - C8 10 {2}^{2}{3}^{8}\dfrac{1}{{x}^{2}} . . . . . . . = C0 10 {2}^{10}{3}^{0}{x}^{30} + C1 10 {2}^{9}{3}^{1}{x}^{26} . . . . . . . . . . . . . . C7 10 {2}^{3}{3}^{7}{x}^{2}

Put x=1x = 1 both side we get,

510−39(60+20+3)=C01021030+C1102931..............C7102337{5}^{10} - {3}^{9}\left(60 + 20 + 3\right) = C0 10 {2}^{10}{3}^{0} + C1 10 {2}^{9}{3}^{1} . . . . . . . . . . . . . . C7 10 {2}^{3}{3}^{7}

510−39(83)=sum of even coefficients{5}^{10} - {3}^{9}\left(83\right) = \text{sum of even coefficients}

So β=83\beta = 83

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