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If \int \frac{x+1}{\sqrt{2x-1}}dx=f(x)\sqrt{2x-1}+C , where C is a constant of integration, then f(x) is equal to :


Option: 1 \frac{2}{3}(x+2)
Option: 2 \frac{1}{3}(x+1)
Option: 3 \frac{1}{3}(x+4)
Option: 4 \frac{2}{3}(x-4)
 

Answers (1)

best_answer

 

Indefinite integrals for Algebraic functions -

 \frac{\mathrm{d}}{\mathrm{d} x} \frac{\left ( x^{n+1} \right )}{n+1}=x^{n} so \int x^{n}dx=\frac{x^{n+1}}{n+1}

- wherein

Where  n\neq-1

 

 

Integration by substitution -

The functions when on substitution of the variable of integration to some quantity gives any one of standard formulas.

 

 

- wherein

Since \int f(x)dx=\int f(t)dt=\int f(\theta )d\theta all variables must be converted into single variable ,\left ( t\, or\ \theta \right )

 

Let t = \sqrt{2x-1}

=>t^{2}={2x-1}

=>2t\: dt=2\: dx

\int \frac{x+1}{\sqrt{2x-1}}dx=\int \frac{t^{2}+3}{2}dt

                               =\frac{1}{2}\left [ \frac{t^{3}}{3}+3t \right ]

                               =\frac{t}{6}(t^{2}+9)+C

t = \sqrt{2x-1}

 =\frac{\sqrt{2x-1}}{6}(2x+8)+C

=\frac{\sqrt{2x-1}}{3}(x+4)+C

=>f (x)=\frac{x+4}{3}

 

Posted by

Ritika Jonwal

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