Thread: Partial Fraction

I worked it down to

and then

x = 5
a= 1

x = -1
-12 = b

whats confusing me is that if i let x = -1 for c i would get -12 = C0 which is -12 = 0
is my equation wrong?

Originally Posted by x5pyd3rx

I worked it down to

and then

x = 5
a= 1

x = -1
-12 = b

whats confusing me is that if i let x = -1 for c i would get -12 = C0 which is -12 = 0
is my equation wrong?

Never thought about doing the question like that but lets roll with it...

If x=5, everything bu the A term is 0 so we get...

216A = 216.

So A = 1.

If x=-1, everything but the D term cancels and you get...

-6D = -12, D = 2

Now set x to be something generic like 0.

Chances are you'll get something like ...B + ...C = -9

Then set x to be something else. Like 1 for example.

Once again you'll get an equation involving B and C.

Solve for B and C using simultaneous equations.

Alternatively you could see that you'll get Ax^3 + ... + Bx^3 + ...

So B must be equal to 0.

Something tells me that won't work though. You sure that equation is going to work..?

Actually yeah it will be. C=0 as well.