M例6求2 x2-8x+25 解∫ dx x2-8x+25 1dx (x-4)2+9 x-4 3 d x 3 2 工工工 +1 十 3 3 x-4 =arctan +C 3 3 上页例6 求 . 8 2 5 1 2 d x x x  − + 解 d x x x  − 8 + 2 5 1 2 dx x  − + = ( 4) 9 1 2 d x x   +      − = 1 3 4 1 3 1 2 2       −  +      − =  3 4 1 3 4 1 3 1 2 x d x . 3 4 arctan 3 1 C x + − =