已知4x²+y²-4x+6y+10=0, 求4x²-12xy+9y²的值
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已知4x²+y²-4x+6y+10=0, 求4x²-12xy+9y²的值
已知4x²+y²-4x+6y+10=0, 求4x²-12xy+9y²的值
已知4x²+y²-4x+6y+10=0, 求4x²-12xy+9y²的值
配方得 (2x-1)^2+(y+3)^2=0 ,
因此 2x-1=0 ,y+3=0 ,
解得 x=1/2 ,y= -3 ,
所以 4x^2-12xy+9y^2=4*(1/2)^2-12*(1/2)*(-3)+9*(-3)^2=1+18+81=100 .