已知x²-y²=20,x+y=-5求y-x的值
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已知x²-y²=20,x+y=-5求y-x的值
已知x²-y²=20,x+y=-5求y-x的值
已知x²-y²=20,x+y=-5求y-x的值
x²-y²=(x+y)*(x-y)=-5*(x-y)=20
所以:x-y=-4;
y-x=4
x^2-y^2=(x+y)(x-y)=20
又x+y=-5
所以x-y=-4
所以y-x=4
(X+Y)(X-Y)=20
X+Y=-5
两等式两边相除得:
X-Y=-4
Y-X=4
x^2-y^2=(x+y)(x-y)=20
x+y=-5
x-y=-4
y-x=4
x²-y²=(x+y)(x-y)=20,把x+y=-5代入,消去,的x-y=-4,所以y-x=4