Solution.(1)∵∫=2x1x2+4x1x3-x2+6x2x3+4x3 0 2 AY2 3 34 012 f=x v 3 \2 3 4LX3 1-13 2 20 (2)∵A=-205 05-3 ∫=x1-4x1x2+10x2x3-3 K心Solution. (1) 2 4 6 4 2 2 3 3 2  f = x1x2 + x1x3 − x2 + x x + x            = − 2 3 4 1 1 3 0 1 2 A                       = − 3 2 1 1 2 3 2 3 4 1 1 3 0 1 2 x x x f x x x           − − − = 0 5 3 2 0 5 1 2 0 (2)  A 4 10 3 . 2 1 2 2 3 3 2  f = x1 − x x + x x − x