已知X2+4y2-4x+4y+5=0 求x-y的值 已知xy=4满足x2y-xy2-x+y=56,求x2+y2的值
问题描述:
已知X2+4y2-4x+4y+5=0 求x-y的值 已知xy=4满足x2y-xy2-x+y=56,求x2+y2的值
答
x²+4y²-4x+4y+5=0(x-2)²+(2y+1)²=0x-2=0 x=22y+1=0 y=-1/2x-y=2+1/2=5/2x²y-xy²-x+y=56xy(x-y)-(x-y)=56(x-y)(xy-1)=56(x-y)(4-1)=563(x-y)=56x-y=56/3x²+y²=(x-y)²+2...