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MHT CET · Maths · Indefinite Integration

If
\(\int(7 x-2) \sqrt{3 x+2} \mathrm{~d} x=\mathrm{A}(3 x+2)^{\frac{5}{2}}+\mathrm{B}(3 x+2)^{\frac{3}{2}}+\mathrm{c}\)
(where c is a constant of integration), then the values of \(A\) and \(B\) are respectively

  1. A \(\frac{14}{45}, \frac{40}{27}\)
  2. B \(\frac{14}{15}, \frac{-40}{9}\)
  3. C \(\frac{14}{15}, \frac{40}{9}\)
  4. D \(\frac{14}{45}, \frac{-40}{27}\)
Verified Solution

Answer & Solution

Correct Answer

(D) \(\frac{14}{45}, \frac{-40}{27}\)

Step-by-step Solution

Detailed explanation

Let \(\mathrm{I}=\int(7 x-2) \sqrt{3 x+2} \mathrm{~d} x\)
Let \(3 x+2=\mathrm{t} \Rightarrow x=\frac{\mathrm{t}-2}{3} \Rightarrow \mathrm{~d} x=\frac{1}{3} \mathrm{dt}\)
\(\therefore \mathrm{I} \)
\( =\int\left[7\left(\frac{\mathrm{t}-2}{3}\right)-2\right] \sqrt{\mathrm{t}} \mathrm{dt} \)
\( =\frac{1}{3} \int\left(\frac{7 \mathrm{t}}{3}-\frac{20}{3}\right) \sqrt{\mathrm{t}} \mathrm{dt} \)
\( =\frac{7}{9} \int \mathrm{t}^{\frac{3}{2}} \mathrm{dt}-\frac{20}{9} \int \mathrm{t}^{\frac{1}{2}} \mathrm{dt} \)
\( =\frac{14}{45}(3 x+2)^{\frac{5}{2}}-\frac{40}{27}(3 x+2)^{\frac{3}{2}}+\mathrm{C} \)
\( \therefore A=\frac{14}{45} \text { and } B=\frac{-40}{27}\)