已知x-y=2,则x2-y2-4y=______.
已知x2+4x+y2-2y+5=0,则x2+y2=______.
已知x-y=2,则x2-y2-4y=______.
已知x2-4y2=20,x+2y=5,则x=______,y=______.
已知x+y=4,xy=2,则x2+y2+3xy=______.
已知x+y=4,x2+y2=10,则(x-y)2=______.
已知x2+y2+z2-2x+4y-6z+14=0,则x+y+z=______.
已知实数x、y满足(x2+y2)(x2+y2-1)=2,则x2+y2的值为______.
(选做题)已知x+2y=1,则x2+y2的最小值是______.
已知实数x、y满足x2+4xy+4y2+x+2y-6=0,则x+2y的值为______.
已知实数x,y满足2x+y≥1,则u=x2+y2+4x-2y的最小值为______.
已知:x+y=4,x2-y2=20,则x-y的值是______.
已知x-y=5,(x+y)2=49,则x2+y2的值等于______.