若x^2-4y^2=-15,2y-x=5,则x+2y=____
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若x^2-4y^2=-15,2y-x=5,则x+2y=____若x^2-4y^2=-15,2y-x=5,则x+2y=____若x^2-4y^2=-15,2y-x=5,则x+2y=____x^2-4y^
若x^2-4y^2=-15,2y-x=5,则x+2y=____
若x^2-4y^2=-15,2y-x=5,则x+2y=____
若x^2-4y^2=-15,2y-x=5,则x+2y=____
x^2-4y^2
=(x+2y)(x-2y)
=(x+2y)*(-5)
=-15
所以
x+2y=3
3
3
由方程2得 x=2y-5
代入1得 y=2
所以x=3
所以x+2y=7
x^2-4y^2=(x+2y)(x-2y)=-5(x+2y)=15 所以x+2y=3
因为x^2-4y^2=(x+2y)(x-2y)=-15;
又有x-2y=-5;(由2y-x=5得来)
所以x+2y=-15/-5=3。
若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值
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x*x+2x+y*y-4y+5=0 x= y=
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