若x2-y2=20,且x+y=-5,则x-y的值是______.
若x,y∈R且x2+y2=1,则x-y的取值范围为______.
已知:x+y=4,x2-y2=20,则x-y的值是______.
已知x、y是实数且满足x2+xy+y2-2=0,设M=x2-xy+y2,则M的取值范围是______.
设x,y≠0,且方程(x2+xy+y2)a=x2-xy+y2成立,则实数a的取值范围是______.
若实数x,y满足x2+4y2=4x,则S=x2+y2的取值范围是______.
已知x2+y2=25,x+y=7,且x>y,则x-y的值等于______.
若(x+y)2=25,(x-y)2=1,x2+y2的值是______.
若实数x,y满足3x2+2y2=6x,则x2+y2的最大值为______.
已知x2+4x+y2-2y+5=0,则x2+y2=______.
已知x-y=5,(x+y)2=49,则x2+y2的值等于______.
若实数x,y满足2x2+3y2=1,S=3x2-2y2,则S的取值范围是______.
2010.09.已知x、y为实数,且(x2+y2)(x2+y2+1)=20,求x2+y2的值