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If the integral I=∫[loge(logex)2+alogex]dx=xloge(logex)2+CI = \int \left[log_e(log_e x)^2 + \frac{a}{log_e x}\right] dx = x log_e(log_e x)^2 + C, where C is constant of integration. Then the value of aa is:

Solution

✅ Correct Option: 4

Given that I=∫[log⁡e(log⁡ex)2+alog⁡ex]dx=xlog⁡e(log⁡ex)2+CI = \int \left[\log_e(\log_e x)^2 + \frac{a}{\log_e x}\right] dx = x \log_e(\log_e x)^2 + C

If ∫f(x)dx=F(x)+C\int f(x) dx = F(x) + C, then ddx[F(x)]=f(x)\frac{d}{dx}[F(x)] = f(x)

Differentiating both sides with respect to xx:

log⁡e(log⁡ex)2+alog⁡ex=ddx[xlog⁡e(log⁡ex)2]\log_e(\log_e x)^2 + \frac{a}{\log_e x} = \frac{d}{dx}\left[x \log_e(\log_e x)^2\right]


Using the product rule on the right side:

ddx[xlog⁡e(log⁡ex)2]\frac{d}{dx}\left[x \log_e(\log_e x)^2\right]

=(1)⋅log⁡e(log⁡ex)2+x⋅ddx[log⁡e(log⁡ex)2]= (1) \cdot \log_e(\log_e x)^2 + x \cdot \frac{d}{dx}\left[\log_e(\log_e x)^2\right]


For ddx[log⁡e(log⁡ex)2]\frac{d}{dx}\left[\log_e(\log_e x)^2\right], using the chain rule:

ddx[log⁡e(log⁡ex)2]\frac{d}{dx}\left[\log_e(\log_e x)^2\right]

=1(log⁡ex)2⋅ddx[(log⁡ex)2]= \frac{1}{(\log_e x)^2} \cdot \frac{d}{dx}\left[(\log_e x)^2\right]

=1(log⁡ex)2⋅2log⁡ex⋅1x= \frac{1}{(\log_e x)^2} \cdot 2\log_e x \cdot \frac{1}{x}

=2xlog⁡ex= \frac{2}{x \log_e x}


Substituting back:

ddx[xlog⁡e(log⁡ex)2]\frac{d}{dx}\left[x \log_e(\log_e x)^2\right]

=log⁡e(log⁡ex)2+x⋅2xlog⁡ex= \log_e(\log_e x)^2 + x \cdot \frac{2}{x \log_e x}

=log⁡e(log⁡ex)2+2log⁡ex= \log_e(\log_e x)^2 + \frac{2}{\log_e x}


Equating both sides:

log⁡e(log⁡ex)2+alog⁡ex=log⁡e(log⁡ex)2+2log⁡ex\log_e(\log_e x)^2 + \frac{a}{\log_e x} = \log_e(\log_e x)^2 + \frac{2}{\log_e x}

Comparing coefficients:

alog⁡ex=2log⁡ex\frac{a}{\log_e x} = \frac{2}{\log_e x}

Therefore, a=2a = 2

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