Author Topic: partial fraction help  (Read 776 times)

Offline nipuna92

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partial fraction help
« on: October 18, 2009, 03:18:40 pm »
please anyone can do this
because i cannot remember

please try to include every step in your answer

Offline astarmathsandphysics

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Re: partial fraction help
« Reply #1 on: October 18, 2009, 10:35:25 pm »
I will answer this when my internet goes back up. There is some fault now and i am on a phone.

Offline nipuna92

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Re: partial fraction help
« Reply #2 on: October 19, 2009, 09:57:05 am »
ok
no hurry take ur time.

Offline slvri

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Re: partial fraction help
« Reply #3 on: October 19, 2009, 11:21:11 am »
ok.......so 100/(x2)(10-x) can be written in the form A/x2+B/x+C(10-x) where A, B and C are constants whose values are to be found
100/(x2)(10-x)=A/(x2)+B/x+C/(10-x)...........(X)
now the trick is first find the values of A and C by substituting an appropriate value of x, then find B by a algebraic method
to find A, first multiply every term of (X) by x2
100/(10-x)=A+Bx+Cx2/(10-x)
now put x=0
100/10=A+0+0
A=10
to find C, first multiply every term of (X) by (10-x)
100/(x2)=A(10-x)/(x2)+B(10-x)/x+C
now put x=10
1=0+0+C
C=1
now to find B first put values of A and C in (X)
100/(x2)(10-x)=10/(x2)+B/x+1/(10-x)
100/(x2)(10-x)=[10(10-x)+Bx(10-x)+x2)]/(x2(10-x)
100/(x2)(10-x)=[100-10x+10Bx-Bx2+x2]/(x2(10-x)
multiply by x2(10-x) and simplify
100=100+(10B-10)x+(1-B)x2
100+0x+0x2=100+(10B-10)x+(1-B)x2
coefficient of x must be 0
10B-10=0
10B=10
B=1
coefficient of x2must be 0
1-B=0
B=1
so 100/(x2)(10-x)=10/(x2)+1/x+1/(10-x)
is this correct?
« Last Edit: October 19, 2009, 01:26:58 pm by astarmathsandphysics »
i hate A level...........

Offline astarmathsandphysics

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Re: partial fraction help
« Reply #4 on: October 19, 2009, 01:30:16 pm »
I think so