x+y=8,xy=-2,求(5xy+4x+7y)+(6x-3xy)-(4xy-3y)的值

三星手机882022-10-04 11:39:541条回答

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詹姆斯_james 共回答了22个问题 | 采纳率90.9%: (5xy+4x+7y)+(6x-3xy)-(4xy-3y)
= 5xy + 4x + 7y + 6x - 3xy - 4xy + 3y
= (5xy - 3xy -4xy) + (4x + 6x) + (7y + 3y)
= -2xy + 10x + 10y
= -2xy + 10(x+y)
= 4 + 80
= 84; 1年前

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x的相反数为y-6,y的倒数为2x
x+y=6 2xy=1
(5xy+4x+7y)+3(2x-xy)-(4xy-3y)
=5xy+4x+7y+6x-3xy-4xy+3y
=-2xy+10x+10y
=10(x+y)-2xy
=60-1
=59

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