若丨2x-5丨+(2x-5y+20)^2=0,求代数式(-2x^2)-2x(5y-2x)=3y(6x-5y)-3y(4x-5y)的值

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若丨2x-5丨+(2x-5y+20)^2=0
∴2x-5=0;
x=5/2;
2x-5y+20=0;
y=5;
(-2x^2)-2x(5y-2x)-3y(6x-5y)-3y(4x-5y)
=-2x²-10xy+4x²-18xy+15y²-12xy+15y²
=2x²+30y²-40xy
=2*(25/4)+30*25-40*(5/2)*5
=25/2+750-500
=250+25/2
=262.5

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