Friday, April 10, 2015

Show how to evaluate the indefinite integral of function y=1/(x^2-x)?

We'll use partial fraction decomposition to evaluate the
given integral.


We'll first factorize the
denominator:


1/(x^2 - x) =
1/x(x-1)


Now, we'll re-write the fraction 1/ ( x^2 - x ) as
an algebraic sum of irreducible fractions.


1/(x^2 - x) =
A/x + B/(x-1)


1 = A(x-1) +
Bx


1 = Ax - A + Bx


1 = x(A+B)
- A


A+B = 0 =>
A=-B


-A=1 => A=-1
=>B=1


1/(x^2 - x) = -1/x +
1/(x-1)


Now, we'll evaluate the
integral:


`int` dx/ ( x^2 - x ) = -`int` dx/x + `int`
dx/(x-1)


`int` dx/ ( x^2 - x ) = -ln|x| + ln|x-1| +
C


We'll use the quotient property of
logarithms:


`int` dx/ ( x^2 - x ) = ln|(x-1)/x| +
C


The requested indefinite integral is: `int`
dx/ ( x^2 - x ) = ln|(x-1)/x| + C

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