Test Index

NCERT Class XII Mathematics Chapter - - Solutions

Show Para  Hide Para 
..... Miscellaneous Exercise .....
Integrate the functions in Exercises 229 to 252.
© examsnet.com
Question : 234 of 271
Marks: +1, -0
5x(x+1)(x2+9)\frac{5x}{(x+1)(x^2+9)}
Solution:  
Let I=5x(x+1)(x2+9)dxI = \frac{5x}{(x+1)(x^2+9)}dx
Let 5x(x+1)(x2+9)\frac{5x}{(x+1)(x^2+9)} =Ax+1+Bx+Cx2+9= \frac{A}{x+1} + \frac{Bx+C}{x^2+9}
⇒5x=A(x2+9)+(Bx+C)(x+1)\Rightarrow 5x = A(x^2+9) + (Bx+C)(x+1) ... (i)
Let x+1=0⇒x=−1x+1=0 \Rightarrow x=-1
∴ 5(-1) = A(1 + 9) ⇒ A =−12= -\frac{1}{2}
Comparing coefficient of x2x^2 in (i), we get 0=A+B⇒B=120 = A + B \Rightarrow B = \frac{1}{2}
Let x=0x = 0 ⇒0=9A+C\Rightarrow 0 = 9A + C ⇒C=92\Rightarrow C = \frac{9}{2}
∴I=∫−12x+1dx+∫12x+92x2+9dx\therefore I = \int \frac{-\frac{1}{2}}{x+1}dx + \int \frac{\frac{1}{2}x + \frac{9}{2}}{x^2+9}dx
=−12log⁡(x+1)+14∫2xx2+9dx+92∫dxx2+32+C= -\frac{1}{2}\log(x+1) + \frac{1}{4}\int \frac{2x}{x^2+9}dx + \frac{9}{2}\int \frac{dx}{x^2+3^2} + C
=−12log⁡(x+1)+14log⁡(x2+9)+92×13tan⁡−1x3+C= -\frac{1}{2}\log(x+1) + \frac{1}{4}\log(x^2+9) + \frac{9}{2} \times \frac{1}{3} \tan^{-1}\frac{x}{3} + C
=−12log⁡(x+1)+14log⁡(x2+9)+32tan⁡−1x3+C= -\frac{1}{2}\log(x+1) + \frac{1}{4}\log(x^2+9) + \frac{3}{2}\tan^{-1}\frac{x}{3} + C
© examsnet.com
Go to Question:
Advertisements