Maths help- partial...
 

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[Closed] Maths help- partial fractions

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Stupid moment here...

Got to put
(-11x+80)/((x^2)-16x+64)
into partial fractions.

Got
A/(x-8) + B/(x-8)
but no idea how to work out A and B?

Any ideas for a muppet?

Ta, Duane.


 
Posted : 09/11/2009 9:11 pm
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I think the fact that you have a "repeated term" [ie. (x-8)^2] in the denominator changes how you do it but I can't for the life of me work out how it goes.

ie. I don't think it's simply

A/(x-8) + B/(x-8)

but

A/[(x-8)^2] + B/(x-8)

but can't remember if it's A or Ax + C on top of your first partial fraction.

Hopefully *some* help? 😯


 
Posted : 09/11/2009 9:27 pm
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42


 
Posted : 09/11/2009 9:27 pm
 MS
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Doing an engineering degree, think this is how u do it.

Its like munkster said

A/(x-8)^2 + B/(x-8)

Then you just work out A and B in the normal way

Cheers


 
Posted : 09/11/2009 9:48 pm
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Ah yes, thought I was right but I couldn't get it to work but have just done it...

So

A/(x-8)^2 + B/(x-8)

Multiply second fraction by (x-8) top and bottom

A/(x-8)^2 + B(x-8)/(x-8)^2

Write as one fraction and expand/collect numerator

(A - 8B + Bx)/(x-8)^2

Equate numerator to numerator of original and compare coefficients/constants

So B = -11 and A - 8B = 80

but B = -11 so A + 88 = 80 and A = -8

Works innit... 😉


 
Posted : 09/11/2009 9:54 pm
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Thanks a ton mate, worked it out after your first post, cheers 🙂


 
Posted : 09/11/2009 10:16 pm