Question:

Let $f(x)=\int \frac{2 x}{\left(x^2+1\right)\left(x^2+3\right)} d x$. If $f(3)=\frac{1}{2}\left(\log _e 5-\log _e 6\right)$, then $f(4)$ is equal to

Updated On: Mar 4, 2024
  • $\log _{ e } 17-\log _{ e } 18$
  • $\log _e 19-\log _e 20$
  • $\frac{1}{2}\left(\log _e 19-\log _e 17\right)$
  • $\frac{1}{2}\left(\log _e 17-\log _e 19\right)$
Hide Solution
collegedunia
Verified By Collegedunia

The Correct Option is D

Solution and Explanation

The correct option is (D) : \(\frac{1}{2}\left(\log _e 17-\log _e 19\right)\)
Put x2=t 
\(\frac{dt}{(t+1)(t+3)}\)
​=\(\frac{1}{2}\)​∫(\(\frac{1}{t+1}\)​−\(\frac{1}{t+3}\)​)dt 
f(x)=\(\frac{1}{2}\)​ln(\(\frac{x^2+1}{x^2+3}\))+C 
f(3)=\(\frac{1}{2}\)​(ln10−ln12)+C 
⇒C=0 
f(4)=\(\frac{1}{2}\)​ln(\(\frac{17}{19}\)​)

Was this answer helpful?
0
0

Questions Asked in JEE Main exam

View More Questions

Concepts Used:

Integrals of Some Particular Functions

There are many important integration formulas which are applied to integrate many other standard integrals. In this article, we will take a look at the integrals of these particular functions and see how they are used in several other standard integrals.

Integrals of Some Particular Functions:

  • ∫1/(x2 – a2) dx = (1/2a) log|(x – a)/(x + a)| + C
  • ∫1/(a2 – x2) dx = (1/2a) log|(a + x)/(a – x)| + C
  • ∫1/(x2 + a2) dx = (1/a) tan-1(x/a) + C
  • ∫1/√(x2 – a2) dx = log|x + √(x2 – a2)| + C
  • ∫1/√(a2 – x2) dx = sin-1(x/a) + C
  • ∫1/√(x2 + a2) dx = log|x + √(x2 + a2)| + C

These are tabulated below along with the meaning of each part.