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Find \(\int \frac{20x^3}{1+x^4} dx\).(a) 5 log(x^4)+C(b) -5 log(1+x^4)+C(c) 5 log(1+x^4)+C(d) log(1+x^4)+CI had been asked this question in class test.My question is taken from Methods of Integration-1 in division Integrals of Mathematics – Class 12 |
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Answer» CORRECT ANSWER is (c) 5 log(1+x^4)+C To ELABORATE: Let 1+x^4=t 4x^3 dx=DT ∴\(\int \frac{20x^3}{1+x^4} dx=5\int \frac{dt}{t}\) =5 logt Replacing t with 1+x^4, we get \(\int \frac{20x^3}{1+x^4} dx=5 \,log(1+x^4)+C\) |
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