已知x+y=3,xy=-2,求(3x-4y+2xy)-(2x-5y+5xy)的值请说明为什么这么做
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已知x+y=3,xy=-2,求(3x-4y+2xy)-(2x-5y+5xy)的值请说明为什么这么做
已知x+y=3,xy=-2,求(3x-4y+2xy)-(2x-5y+5xy)的值
请说明为什么这么做
已知x+y=3,xy=-2,求(3x-4y+2xy)-(2x-5y+5xy)的值请说明为什么这么做
(3x-4y+2xy)-(2x-5y+5xy)
=3x-4y+2xy-2x+5y-5xy
=x+y-3xy
=3-3•(-2)
=3+6
=9
第一步肯定要去括号,这样才能化简
第二步,合并同类项.