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Evaluate the integral of \int\frac{x^{2}-1}{x^{2}-9}dx

 

Option: 1

x+\frac{4}{3}ln\frac{\left | x-3 \right |}{\left | x+3 \right |}+C


Option: 2

x-\frac{4}{3}ln\frac{\left | x-3 \right |}{\left | x+3 \right |}+C


Option: 3

x+\frac{4}{3}ln\frac{\left | x+3 \right |}{\left | x-3 \right |}+C


Option: 4

x-\frac{4}{3}ln\frac{\left | x+3 \right |}{\left | x-3 \right |}+C


Answers (1)

best_answer

Given integral,

\int\frac{x^{2}-1}{x^{2}-9}dx

\int\frac{x^{2}-1}{x^{2}-9}dx=\int\left ( 1+\frac{8}{\left ( x+3 \right )\left ( x-3 \right )} \right )dx

\int\frac{x^{2}-1}{x^{2}-9}dx=\int\left ( 1+\frac{A}{x+3}+\frac{B}{x-3} \right)dx

Using partial fractions,

A\left ( x-3 \right )+B\left ( x+3 \right )=8

Put  x=3,

B=\frac{4}{3}

Put x=-3

A=-\frac{4}{3}

Now,

\int\frac{x^{2}-1}{x^{2}-9}dx=\int\left ( 1+\frac{-\frac{4}{3}}{x+3}+\frac{\frac{4}{3}}{x-3} \right)dx

\int\frac{x^{2}-1}{x^{2}-9}dx=x-\frac{4}{3}ln\left | x+3 \right |+\frac{4}{3}ln\left | x-3 \right |+C

\int\frac{x^{2}-1}{x^{2}-9}dx=x+\frac{4}{3}\left ( ln\left | x-3 \right |-ln\left |x+3 \right | \right )+C

\int\frac{x^{2}-1}{x^{2}-9}dx=x+\frac{4}{3}ln\frac{\left | x-3 \right |}{\left | x+3 \right |}+C

Posted by

vishal kumar

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