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NCERT Class XII Mathematics Chapter - - Solutions

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Exercise - 7.5
Integrate the rational functions in Exercises 111 to 131.
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Question : 124 of 271
Marks: +1, -0
3x−1(x+2)2\frac{3x-1}{(x+2)^2}
Solution:  
Let I=∫3x−1(x+2)2dxI=\int \frac{3x-1}{(x+2)^2} dx
Let 3x−1(x+2)2=Ax+2+B(x+2)2\frac{3x-1}{(x+2)^2} = \frac{A}{x+2} + \frac{B}{(x+2)^2}
⇒ 3x – 1 = A(x + 2) + B ...(i)Comparing coefficients of x in (i), we get
A = 3
Comparing the coefficients of constant terms in (i), we get
2A + B = –1 ...(ii)
Put A = 3 in (ii), we get 6 + B = –1 ⇒ B = –7
∴3x−1(x+2)2=3x+2−7(x+2)2\therefore \frac{3x-1}{(x+2)^2} = \frac{3}{x+2} - \frac{7}{(x+2)^2}
∴∫3x−1(x+2)2dx\therefore \int \frac{3x-1}{(x+2)^2} dx =3∫dxx+2−7∫dx(x+2)2= 3 \int \frac{dx}{x+2} - 7 \int \frac{dx}{(x+2)^2}
=3log⁡∣x+2∣−7(x+2)−1−1+C= 3 \log|x+2| - 7 \frac{(x+2)^{-1}}{-1} + C
=3log⁡∣x+2∣+7x+2+C= 3 \log|x+2| + \frac{7}{x+2} + C
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