作业帮先化简再求值:(3x²+y²)-[-3x-2(x²-xy)+y²],其中x=-1,y=-2
来源：学生作业帮助网 编辑：作业帮 时间：2024/07/27 01:34:54
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先化简再求值:(3x²+y²)-[-3x-2(x²-xy)+y²],其中x=-1,y=-2
先化简再求值:(3x²+y²)-[-3x-2(x²-xy)+y²],其中x=-1,y=-2
先化简再求值:(3x²+y²)-[-3x-2(x²-xy)+y²],其中x=-1,y=-2
(3x²+y²)-[-3x-2(x²-xy)+y²]
=3x²+y²+3x+2(x²-xy)-y²
=3x²+y²+3x+2x²-2xy-y²
=5x²+3x-2xy
把x=-1,y=-2代入得：
5-3-4=-2