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Mathematics 7 Online
OpenStudy (ggrree):

http://gyazo.com/7919fbc4610aa7647d33100ee01aec29

OpenStudy (ggrree):

I was able to separate the integrand into partial fractions but then I get stuck.

myininaya (myininaya):

Is that a type-o?

myininaya (myininaya):

\[\int\limits_{0}^{9}\frac{dx}{x^2-6+5}\]

myininaya (myininaya):

Is it really suppose to be x^2-6+5 and not x^2-6x+5?

myininaya (myininaya):

\[\frac{1}{x^2-1} \text{ since } -6+5=-1\] \[\frac{1}{(x-1)(x+1)}=\frac{A}{x-1}+\frac{B}{x+1}\]

myininaya (myininaya):

\[\frac{1}{(x-1)(x+1)}=\frac{A(x+1)+B(x-1)}{(x-1)(x+1)}\] => 1=x(A+B)+(A-B) A+B=0 ; A-B=1

myininaya (myininaya):

Can you do the test now?

myininaya (myininaya):

And by the way this is an improper integral meaning the function is not continuous on [0,9]

myininaya (myininaya):

You will have to break up the integral

myininaya (myininaya):

\[\int\limits_{0}^{1}\frac{dx}{x^2-1} +\int\limits_{1}^{9}\frac{dx}{x^2-1}\]

myininaya (myininaya):

See if both parts converge if so then take the sum in you are done if not then the area/net area is divergent

myininaya (myininaya):

lol I meant rest above not test

myininaya (myininaya):

@ggrree any questions?

OpenStudy (apoorvk):

i think we have a standard formula as well for integrals of this type rather than use partial fractions every time: \[\int\limits(1/(x^2-a^2))dx =(1/2a)\ln((x-a)/(x+a)) + k\]

OpenStudy (apoorvk):

|dw:1332635709657:dw|

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