x2+xy+y2=1,且x,y∈R,则x+y的取值范围
若x2+xy+y2=1且x、y∈R,则n=x2+y2的取值范围是( )
已知x,y∈R,且1≤x2+y2≤2,z=x2+xy+y2,则z的取值范围是
若x,y∈R且x2+y2=1,则x-y的取值范围为______.
设x,y是实数,且 x2+xy+y2=3.那么,x2-xy+y2的取值范围是?
已知x、y∈R,且x2+y2=2,求x+y的取值范围.
设实数x,y满足x2+y2=1则 xy的取值范围是?
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______.
设x,y为实数,且x2+xy+y2=1,求x2-xy+y2的值的范围
设实数xy满足x2 +2y2=6,则x+y的取值范围
已知x,y满足x2/9+y2/4=1,则xy的取值范围是?
已知实数xy满足x2+y2=4.则y+3/x+1的取值范围为