Integral Calculus Question 402

Question: $ \int_{{}}^{{}}{\frac{10x^{9}+10^{x}{\log_{e}}10}{10^{x}+x^{10}}}\ dx= $

[MNR 1979]

Options:

A) $ -\frac{1}{2}\frac{1}{{{(10^{x}+x^{10})}^{2}}}+c $

B) $ \log (10^{x}+x^{10})+c $

C) $ \frac{1}{2}\frac{1}{{{(10^{x}+x^{10})}^{2}}}+c $

D) None of these

Show Answer

Answer:

Correct Answer: B

Solution:

Put $ x^{10}+10^{x}=t\Rightarrow (10x^{9}+10^{x}{\log_{e}}10),dx=dt, $ then $ \int_{{}}^{{}}{\frac{10x^{9}+10^{x}{\log_{e}}10}{10^{x}+x^{10}},dx}=\int_{{}}^{{}}{\frac{1}{t},dt=\log t+c} $ $ =\log (x^{10}+10^{x})+c. $