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已知|3x+y-0.5|+(x+2y+1.5)2=0,求代数式(x-y)(x-2y)-3x(
1
3
x-y)+(2x+y)(2x-y)的值.
人气:184 ℃ 时间:2019-08-19 12:44:09
解答
∵|3x+y-0.5|+(x+2y+1.5)2=0,
∴3x+y-0.5=0,x+2y+1.5=0,
3x+y=
1
2
x+2y=−
3
2

解得:x=
1
2
,y=-1,
∴(x-y)(x-2y)-3x(
1
3
x-y)+(2x+y)(2x-y)
=x2-2xy-xy+2y2-x2+3xy+4x2-y2
=4x2+y2
=4×(
1
2
2+(-1)2
=2.
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