化简求值:(1)-2x-[4x-2y-(3x-2y+1)],其中x=-3,y=2007;(2)xy-2y2-2[4xy-(3y2-x2y)+5(-3y2+25

2025-05-22 07:15:15
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回答1:

(1)原式=-2x-4x+2y+3x-2y+1=-3x+1,
当x=-3时,原式=10;
(2)原式=xy-2y2-8xy+6y2-2x2y+30y2-4x2y=-7xy+34y2-6x2y,
当x=1,y=-2时,原式=162.