Re: [積分] very難
※ 引述《chingyes (axsazxc)》之銘言：
: http://0rz.tw/5b5bZ
: 請問紅線部分
: 如何變過去的
: 請神人指導@@
x - 1 A Bx + C
1. 令 ------------ = --- + ---------
(x)(x^2 + 1) x x^2 + 1
則 x - 1 = (A)(x^2 + 1) + (x)(Bx + C)
= (A + B)(x^2) + Cx + A
A + B = 0 A = -1
C = 1 => B = 1
A = -1 C = 1
x - 1 A B C
2. 令 ------------ = --- + ----- + -------
(x^2)(x + 1) x x^2 x + 1
則 x - 1 = (A)(x)(x + 1) + (B)(x + 1) + (C)(x^2)
= (A + C)(x^2) + (A + B)(x) + B
A + C = 0 A = 2
A + B = 1 => B = -1
B = -1 C = -2
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