先化简再求值:(x-2y)²-(x+2y)(x-2y)-(x-3y)(x-y).其中x²+9y²+4x-18y+13=0.
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先化简再求值:(x-2y)²-(x+2y)(x-2y)-(x-3y)(x-y).其中x²+9y²+4x-18y+13=0.
先化简再求值:(x-2y)²-(x+2y)(x-2y)-(x-3y)(x-y).其中x²+9y²+4x-18y+13=0.
先化简再求值:(x-2y)²-(x+2y)(x-2y)-(x-3y)(x-y).其中x²+9y²+4x-18y+13=0.
x²+9y²+4x-18y+13=0.
(x²+4x)+(9y²-18y)+(4+9)=0
(x²+4x+4)+(9y²-18y+9)=0
(x+2)²+9(y-1)²=0
则x=2 y=1
原式=(2-2X1)²-(2+2X1)(2-2X1)-(2-3X1)(2-1)=1 [X为乘号]
已知x²+9y²+4x-18y+13=0
可得:x²+4x+4+9y²-18y+9=0
即:(x+2)²+(3y-3)²=0
x=-2,y=1
化简(x-2y)²-(x+2y)(x-2y)-(x-3y)(x-y)
=x²-4xy+4y²-x²+4y²-x²+xy+3xy-3y²
=-x²+5y²
=-4+5=1