- #1
Hypochondriac
- 35
- 0
Im going to Durham uni in oct to do physics, and the nice people of the physics department sent me some maths questions to do before I arrive.
One of the partial fractions questions looked simple enough, but when I did it, I got it wrong...so with the answer they give, i worked back to the question, and they didnt match so I was wondering if it was something I did wrong, or something they did
the question was express (4x+1)/(x+1)^2(x-2) in partial fractions.
so i did the usual 4x+1 ≡ A(x+1)(x-2) + B(x+1)^2(x-2) + C(x+1)^3
then I chose to substitute x=2, as to eliminate A and B,
when I did this I got 9 = 27C, so C = 1/3
in the answer they wouldnve had C as 1.
Their full answer for the record was:
1/(x+1)^2 - 1/(x+1) + 1/(x-2)
but when substituting 1, -1 and 1 in for A B and C, I get 4x^2 + 4x +1 instead of just 4x+1...
whos wrong?
One of the partial fractions questions looked simple enough, but when I did it, I got it wrong...so with the answer they give, i worked back to the question, and they didnt match so I was wondering if it was something I did wrong, or something they did
the question was express (4x+1)/(x+1)^2(x-2) in partial fractions.
so i did the usual 4x+1 ≡ A(x+1)(x-2) + B(x+1)^2(x-2) + C(x+1)^3
then I chose to substitute x=2, as to eliminate A and B,
when I did this I got 9 = 27C, so C = 1/3
in the answer they wouldnve had C as 1.
Their full answer for the record was:
1/(x+1)^2 - 1/(x+1) + 1/(x-2)
but when substituting 1, -1 and 1 in for A B and C, I get 4x^2 + 4x +1 instead of just 4x+1...
whos wrong?