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MHT CET · Maths · Indefinite Integration

\(\int \frac{1}{x^{\frac{1}{2}}+x^{\frac{1}{3}}} d x=\)

  1. A \(\sqrt{x}-\sqrt[3]{x}+\sqrt[6]{x}-\log |\sqrt[6]{x}+1|+c\)
  2. B \(2 \sqrt{x}-3 \sqrt[3]{x}+6 \sqrt[6]{x}-6 \log |\sqrt[6]{x}+1|+c\)
  3. C \(2 \sqrt{x}+3 \sqrt[3]{x}+6 \sqrt[6]{x}+6 \log |\sqrt[6]{x}+1|+c\)
  4. D \(\sqrt{x}+\sqrt[3]{x}+\sqrt[6]{x}+\log |\sqrt[6]{x}+1|+c\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(2 \sqrt{x}-3 \sqrt[3]{x}+6 \sqrt[6]{x}-6 \log |\sqrt[6]{x}+1|+c\)

Step-by-step Solution

Detailed explanation

Let \(I=\int \frac{d x}{x^{\frac{1}{2}}+x^{\frac{1}{3}}}\)
Put \(x^{\frac{1}{6}}=t \Rightarrow x=t^6 \Rightarrow d x=6 t^5\) dt.
Also \(x^{\frac{1}{2}}=t^3\) and \(x^{\frac{1}{3}}=t^2\)
\(I=6 \int \frac{t^5 d t}{t^2(1+t)} \)
\( =6 \int \frac{t^3}{(1+t)} d t=6 \int \frac{\left(t^3+1\right)-1}{(1+t)}=\) \(6 \int \frac{(t+1)\left(t^2-t+1\right)}{(1+t)} d t-6 \int \frac{d t}{1+t} \)
\( =6 \int\left(t^2-t+1\right) d t-6 \log |1+t|+\) \(c=\frac{6 t^3}{3}-\frac{6 t^2}{2}+6 t-6[\log |1+t|]+c \)
\( =2 \sqrt{x}-3 \sqrt[3]{x}+6 \sqrt[6]{x}-6 \log |1+\sqrt[6]{x}|+c\)