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Provide Solution For R.D.Sharma Maths Class 12 Chapter 18  Indefinite Integrals Exercise  Revision Exercise Question 51 Maths Textbook Solution.

Answers (1)

Answer:

I=\frac{1}{2} \ln \left(\mathrm{x}^{2}+4 \mathrm{x}+5\right)-\tan ^{-1}(\mathrm{x}+2)+\mathrm{c}

Given:

\int \frac{x+1}{x^{2}+4 x+5} d x

Hint:

To solve this equation we will make term into differential form.

Solution: 

\int \frac{x+1}{x^{2}+4 x+5} d x

  I=\int \frac{x+2-1}{x^{2}+4 x+5} d x                        

I=\int \frac{x+2}{x^{2}+4 x+5} d x-\int \frac{d x}{x^{2}+4 x+5}

\text { Let } x^{2}+4 x+5=t

(2 x+4) d x=d t

(x+2) d x=\frac{d t}{2}

I=\int \frac{\frac{d t}{2}}{t}-\int \frac{d x}{x^{2}+4 x+4+1}

I=\frac{1}{2} \int \frac{d t}{t}-\int \frac{d x}{(x+2)^{2}+1}

I=\frac{1}{2} \ln (t)-\int \frac{d u}{u^{2}+1} \quad[\because x+2=u, d x=d u]

I=\frac{1}{2} \ln \left(x^{2}+4 x+5\right)-\tan ^{-1} u+c

I=\frac{1}{2} \ln \left(x^{2}+4 x+5\right)-\tan ^{-1}(x+2)+c

 

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