Partial Fractions

Solve (2x/x+1)- (x+7/x^2-x-2) can be written in form A -B/x-2.
Answers: A=2 B=3
I did long division and got A is 2 but i have no idea how to get B after that, because i am left with a quadratic on top and cubic on the bottom after the long division :frown:

:frown:

(edited 9 years ago)

Original post by Nirm

Solve (2x/x+1)- (x+7/x^2-x-2) can be written in form A-B/x-2.
Answers: A=2 B=3
I did long division and got A is 2 but i have no idea how to get B after that, because i am left with a quadratic on top and cubic on the bottom after the long division :frown:

:frown:

Can you post your working up to the point you get stuck?

OP

Original post by notnek

Can you post your working up to the point you get stuck?

Okay so i do: 2x^3 -3x^2 -12x -7 divided by x^3 -3x -2 and end up with 2 remainder -3x^2 -6x -7. Now i have no idea what to do basically. :confused:

:confused:

( I am doing Double)Maths is such a big jump from Gcse to A-levels

(edited 9 years ago)

Original post by Nirm

Okay so i do: 2x^3 -3x^2 -12x -7 divided by x^3 -3x -2 and end up with 2 remainder -3x^2 -6x -7. Now i have no idea what to do basically. :confused:

:confused:

( I am doing Double)Maths is such a big jump from Gcse to A-levels

You are subtracting the fractions by cross multiplying but that isn't always the most efficient way. Factorising gives

\displaystyle \frac{2x}{x+1}- \frac{x+7}{x^2-x-2} = \frac{2x}{x+1}- \frac{x+7}{(x+1)(x-2)}

Try subtracting them again without just cross multiplying.

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