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JEE Main 202529 JanuaryEvening Shift
Exam
JEE Main
Year
2025
Date
29 January
Shift
Evening Shift
Subject
Mathematics
Chapter
Limits

JEE Main 2025 · 29 January · Evening Shift · Mathematics · Limits

If _ t arrow 0 (∫_0^1(3 x+5)^ t d x)^ (1)/(t) = α 5 e ((8)/(5))^...

If lim⁡t→0(∫01(3x+5)tdx)1t=α5e(85)23\lim _{\mathrm{t} \rightarrow 0}\left(\int_0^1(3 x+5)^{\mathrm{t}} \mathrm{d} x\right)^{\frac{1}{t}}=\frac{\alpha}{5 \mathrm{e}}\left(\frac{8}{5}\right)^{\frac{2}{3}}, then α\alpha is equal to ________

Correct answer

0

Step-by-step solution

α5e=exp⁡(lim⁡t→01t(∫01(3x+5)tdx−1))=exp⁡(lim⁡t→01t((3x+5)t+13(t+1))01−1)=exp⁡(lim⁡t→01t(8t+1−5t+13(t+1)−1))=exp⁡(lim⁡t→01t(8t+1−5t+1−3t−33(t+1)))=exp⁡(lim⁡t→0(8t+1⋅ln⁡8−5t+1ln⁡5−33(t+1)))=exp⁡(ln⁡88−ln⁡55−35)\begin{aligned} \frac{\alpha}{5 e} & =\exp \left(\lim _{t \rightarrow 0} \frac{1}{t}\left(\int_0^1(3 x+5)^t d x-1\right)\right) \\ & =\exp \left(\lim _{t \rightarrow 0} \frac{1}{t}\left(\frac{(3 x+5)^{t+1}}{3(t+1)}\right)_0^1-1\right) \\ & =\exp \left(\lim _{t \rightarrow 0} \frac{1}{t}\left(\frac{8^{t+1}-5^{t+1}}{3(t+1)}-1\right)\right) \\ & =\exp \left(\lim _{t \rightarrow 0} \frac{1}{t}\left(\frac{8^{t+1}-5^{t+1}-3 t-3}{3(t+1)}\right)\right) \\ & =\exp \left(\lim _{t \rightarrow 0}\left(\frac{8^{t+1} \cdot \ln 8-5^{t+1} \ln 5-3}{3(t+1)}\right)\right) \\ & =\exp \left(\frac{\ln 8^8-\ln 5^5-3}{5}\right)\end{aligned}=(85)2/3α5e=exp⁡(ln⁡(8855)5−1)⇒(85)2/3α5=(8855)1/3=(86⋅8253⋅52)1/3=645(85)2/3⇒α=64\begin{aligned} & =\left(\frac{8}{5}\right)^{2 / 3} \frac{\alpha}{5 e}=\exp \left(\frac{\ln \left(\frac{8^8}{5^5}\right)}{5}-1\right) \\ & \Rightarrow\left(\frac{8}{5}\right)^{2 / 3} \frac{\alpha}{5}=\left(\frac{8^8}{5^5}\right)^{1 / 3}=\left(\frac{8^6 \cdot 8^2}{5^3 \cdot 5^2}\right)^{1 / 3}=\frac{64}{5}\left(\frac{8}{5}\right)^{2 / 3} \\ & \Rightarrow \alpha=64\end{aligned}$
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