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Definite Integration question

2023 · 11 Apr · Shift 1 · Q43
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Definite Integration question

2023 · 11 Apr · Shift 1 · Q43

JEE MainMathematicsDefinite IntegrationNumerical+4 / −1
For m,n>0m, n \gt 0m,n>0, let α(m,n)=∫02tm(1+3t)ndt\alpha(m, n)=\int_{0}^{2} t^{m}(1+3 t)^{n} d tα(m,n)=∫02​tm(1+3t)ndt. If 11α(10,6)+18α(11,5)=p(14)611 \alpha(10,6)+18 \alpha(11,5)=p(14)^{6}11α(10,6)+18α(11,5)=p(14)6, then ppp is equal to ‾\underline{\hspace{2cm}}​.
Numerical answer
View written solutionFree

Correct answer: 32

  1. We are given
α(m,n)=∫02tm(1+3t)n dt\alpha(m,n)=\int_0^2 t^m(1+3t)^n\,dtα(m,n)=∫02​tm(1+3t)ndt

and need to evaluate

11α(10,6)+18α(11,5).11\alpha(10,6)+18\alpha(11,5).11α(10,6)+18α(11,5).
  1. Substitute the definition of α\alphaα:
11α(10,6)+18α(11,5)=11∫02t10(1+3t)6dt+18∫02t11(1+3t)5dt.11\alpha(10,6)+18\alpha(11,5) =11\int_0^2 t^{10}(1+3t)^6dt+18\int_0^2 t^{11}(1+3t)^5dt.11α(10,6)+18α(11,5)=11∫02​t10(1+3t)6dt+18∫02​t11(1+3t)5dt.

Combine into one integral:

=∫02[11t10(1+3t)6+18t11(1+3t)5]dt.=\int_0^2 \left[11t^{10}(1+3t)^6+18t^{11}(1+3t)^5\right]dt.=∫02​[11t10(1+3t)6+18t11(1+3t)5]dt.

Factor common terms:

=∫02t10(1+3t)5[11(1+3t)+18t]dt.=\int_0^2 t^{10}(1+3t)^5\left[11(1+3t)+18t\right]dt.=∫02​t10(1+3t)5[11(1+3t)+18t]dt.

Now simplify the bracket:

11(1+3t)+18t=11+33t+18t=11+51t.11(1+3t)+18t=11+33t+18t=11+51t.11(1+3t)+18t=11+33t+18t=11+51t.

So,

11α(10,6)+18α(11,5)=∫02t10(1+3t)5(11+51t) dt.11\alpha(10,6)+18\alpha(11,5)=\int_0^2 t^{10}(1+3t)^5(11+51t)\,dt.11α(10,6)+18α(11,5)=∫02​t10(1+3t)5(11+51t)dt.
  1. Notice a derivative pattern:
ddt[t11(1+3t)6]=11t10(1+3t)6+t11⋅6(1+3t)5⋅3.\frac{d}{dt}\left[t^{11}(1+3t)^6\right] =11t^{10}(1+3t)^6+t^{11}\cdot 6(1+3t)^5\cdot 3.dtd​[t11(1+3t)6]=11t10(1+3t)6+t11⋅6(1+3t)5⋅3.

Thus,

ddt[t11(1+3t)6]=11t10(1+3t)6+18t11(1+3t)5.\frac{d}{dt}\left[t^{11}(1+3t)^6\right] =11t^{10}(1+3t)^6+18t^{11}(1+3t)^5.dtd​[t11(1+3t)6]=11t10(1+3t)6+18t11(1+3t)5.

This is exactly the integrand before combining. Therefore,

11α(10,6)+18α(11,5)=∫02ddt[t11(1+3t)6]dt.11\alpha(10,6)+18\alpha(11,5) =\int_0^2 \frac{d}{dt}\left[t^{11}(1+3t)^6\right]dt.11α(10,6)+18α(11,5)=∫02​dtd​[t11(1+3t)6]dt.
  1. Apply the Fundamental Theorem of Calculus:
=[t11(1+3t)6]02.=\left[t^{11}(1+3t)^6\right]_0^2.=[t11(1+3t)6]02​.

At t=2t=2t=2,

211(1+3⋅2)6=211⋅76.2^{11}(1+3\cdot 2)^6=2^{11}\cdot 7^6.211(1+3⋅2)6=211⋅76.

At t=0t=0t=0,

011(1+0)6=0.0^{11}(1+0)^6=0.011(1+0)6=0.

Hence,

11α(10,6)+18α(11,5)=21176.11\alpha(10,6)+18\alpha(11,5)=2^{11}7^6.11α(10,6)+18α(11,5)=21176.
  1. We are told
11α(10,6)+18α(11,5)=p(14)6.11\alpha(10,6)+18\alpha(11,5)=p(14)^6.11α(10,6)+18α(11,5)=p(14)6.

Since

146=(2⋅7)6=26⋅76,14^6=(2\cdot 7)^6=2^6\cdot 7^6,146=(2⋅7)6=26⋅76,

we get

p⋅146=p⋅26⋅76=21176.p\cdot 14^6=p\cdot 2^6\cdot 7^6=2^{11}7^6.p⋅146=p⋅26⋅76=21176.

Cancel 767^676:

p⋅26=211.p\cdot 2^6=2^{11}.p⋅26=211.

So,

p=211−6=25=32.p=2^{11-6}=2^5=32.p=211−6=25=32.
  1. Therefore, the required integer is
32.\boxed{32}.32​.
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