Integral Calculus Question 487

Question: $ \int_{{}}^{{}}{\frac{dx}{4x^{2}+9}=} $

[MP PET 1991; Roorkee 1977; MNR 1974]

Options:

A) $ \frac{1}{2}{{\tan }^{-1}}( \frac{2x}{3} )+c $

B) $ \frac{3}{2}{{\tan }^{-1}}( \frac{2x}{3} )+c $

C) $ \frac{1}{6}{{\tan }^{-1}}( \frac{2x}{3} )+c $

D) $ \frac{1}{6}{{\tan }^{-1}}( \frac{3x}{2} )+c $

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Answer:

Correct Answer: C

Solution:

$ \int_{{}}^{{}}{\frac{dx}{4x^{2}+9}=\frac{1}{4}\int_{{}}^{{}}{\frac{dx}{x^{2}+{{(3/2)}^{2}}}}} $ $ =\frac{1}{4}.\frac{2}{3}.{{\tan }^{-1}}( \frac{2x}{3} )+c=\frac{1}{6}{{\tan }^{-1}}( \frac{2x}{3} )+c. $