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JEE MAIN 2021
25-02-2021 S2
Question
The integral $\int \frac{e^{3 \log _e 2 x}+5 e^{2 \log _e 2 x}}{e^{4 \log _e x}+5 e^{3 \log _e x}-7 e^{2 \log _e x}} d x, x>0$, is equal to :
(where c is a constant of integration)
Select the correct option:
A
$\log _e\left|x^2+5 x-7\right|+c$
B
$4 \log _e\left|x^2+5 x-7\right|+c$
C
$\frac{1}{4} \log _e\left|x^2+5 x-7\right|+c$
D
$\log _e \sqrt{x^2+5 x-7}+c$
✓ Correct! Well done.
✗ Incorrect. Try again or view the solution.
Solution
$\begin{aligned} & \int \frac{e^{3 \log 2 x}+5 e^{2 \log _e 2 x}}{e^{4 \log _e x}+5 e^{3 \log _e x}-7 e^{2 \log _e x}} d x, x>0 \\ & =\int \frac{(2 x)^3+5(2 x)^2}{x^4+5 x^3-7 x^2} d x=\int \frac{4 x^2(2 x+5)}{x^2\left(x^2+5 x-7\right)} d x \\ & =4 \int \frac{d\left(x^2+5 x-7\right)}{\left(x^2+5 x-7\right)}=4 \log _e\left|x^2+5 x-7\right|+c\end{aligned}$
Question Tags
JEE Main
Mathematics
Easy
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