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NCERT Class XII Mathematics Chapter - - Solutions

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Exercise - 7.4
Integrate the functions in Exercises 86 to 108.
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Question : 91 of 271
Marks: +1, -0
x21−x6\frac{x^2}{1-x^6}
Solution:  
Let I=∫x21−x6 dxI=\int \frac{x^2}{1-x^6}\,dx =x21−(x3)2 dx=\frac{x^2}{1-(x^3)^2}\,dx
Put x3=tx^3 = t ⇒3x2 dx=dt\Rightarrow 3x^2\,dx = dt
∴I=13∫dt1−t2\therefore I = \frac{1}{3}\int \frac{dt}{1-t^2} =13⋅12log⁡∣1+t1−t∣+C=\frac{1}{3} \cdot \frac{1}{2} \log \left| \frac{1+t}{1-t} \right| + C
=16log⁡∣1+t1−t∣+C=\frac{1}{6} \log \left| \frac{1+t}{1-t} \right| + C
=16log⁡∣1+x31−x3∣+C=\frac{1}{6} \log \left| \frac{1+x^3}{1-x^3} \right| + C
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