若x-2y=15,xy=-25,求x^2+4y^2-1的值是多少?

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若x-2y=15,xy=-25,求x^2+4y^2-1的值是多少?
若x-2y=15,xy=-25,求x^2+4y^2-1的值是多少?

若x-2y=15,xy=-25,求x^2+4y^2-1的值是多少?
x=15+2y,代入xy=-25,(2y+5）*（y+5）=0,y=-5/2,x=10;y=-5,x=5 x^2+4y^2-1=10^2+4(-5/2)^2-1=124 x^2+4y^2-1=5^2+4(-5)^2-1=124

x=15+2y,代入xy=-25,得（2y+5）*（y+5）=0,y=-5/2,x=10;y=-5,x=5 x^2+4y^2-1=10^2+4(-5/2)^2-1=124 x^2+4y^2-1=5^2+4(-5)^2-1=124

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