Mathematics
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OpenStudy (anonymous):
(x^2+3x)/(x^2-4) partial fraction with steps please
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OpenStudy (kc_kennylau):
\[\frac{x^2+3x}{x^2-4}\equiv\frac{A}{x-2}+\frac{B}{x+2}\]
OpenStudy (anonymous):
I keep getting 1-5/2(x+2)-1/2(x-2)
OpenStudy (kc_kennylau):
wait, i mean:
\[\frac{x^2+3x}{x^2-4}\equiv x\left(\frac A{x-2}+\frac B{x+2}\right)\]
OpenStudy (anonymous):
I don't know what I'm doing wrong
OpenStudy (kc_kennylau):
Ax^2+Bx^2=x^2
2Ax-2Bx=3x
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OpenStudy (kc_kennylau):
A+B=1
2A-2B=3
OpenStudy (kc_kennylau):
2(1)-(2): 4B=-1, B=-0.25
OpenStudy (kc_kennylau):
(1): A=1.25
OpenStudy (kc_kennylau):
\[\frac{x^2+3x}{x^2-4}\equiv\frac{1.25x}{x-2}-\frac{0.25x}{x+2}\]
OpenStudy (kc_kennylau):
what did you get? please use proper brackets
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OpenStudy (anonymous):
The answer says 1+(5/2)(x-2)+1/2(x+2) but I get 1-(5/2)(x+2)-1/2(x-2)
OpenStudy (kc_kennylau):
wait, can you use a divide sign to separate the numerator and the denominator
OpenStudy (kc_kennylau):
i can hardly interpret what you wrote
OpenStudy (anonymous):
5/2 is a fraction as well as 1/2
OpenStudy (rsadhvika):
you need to divide first to make denominator's degree less than numerator
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OpenStudy (anonymous):
I did that
OpenStudy (anonymous):
Hence the 1
OpenStudy (kc_kennylau):
Do you know what you wrote
\[1+\frac52(x-2)+\frac12(x+2)\]
OpenStudy (rsadhvika):
\(\large \frac{x^2+3x}{x^2-4} = \frac{x^2-4 + 4 + 3x}{x^2-4} = 1 + \frac{3x+4}{x^2-4}\)
OpenStudy (anonymous):
Yes I got to that part
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OpenStudy (anonymous):
Wait almost
OpenStudy (rsadhvika):
\(\large \frac{3x+4}{x^2-4} = \frac{A}{x-2} + \frac{B}{x+2}\)
use cover up and find A, B
OpenStudy (anonymous):
I think the signs are different
OpenStudy (anonymous):
That's my mistake
OpenStudy (rsadhvika):
The answer says 1+(5/2)(x-2)+1/2(x+2) but I get 1-(5/2)(x+2)-1/2(x-2)
^^^^^ ^^^^^
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OpenStudy (rsadhvika):
work it again, not just signs.. values above A and B also flipped
OpenStudy (anonymous):
Okay I believe I've done the division in the first step in reverse
Thank you
OpenStudy (rsadhvika):
cool ^_^
OpenStudy (anonymous):
Now I can integrate
OpenStudy (rsadhvika):
yes, that should be trivial, just the ln 's
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OpenStudy (rsadhvika):
:)