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化简求值:已知x、y满足:x2+y2-4x+6y+13=0,求代数式(3x+y)2-3(3x-y)(x+y)-(x-3y)(x+3y)的值.
人气:360 ℃ 时间:2019-10-18 11:36:27
解答
原式=9x2+6xy+y2-3(3x2+3xy-xy-y2)-(x2-9y2) =9x2+6xy+y2-9x2-6xy+3y2-x2+9y2       =-x2+13y2           &n...
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