已知x,y∈R,求证(x2+y2)2≥xy(x+y)2
已知x.y∈R,求证x2+y2+1≥x+y+xy
已知x>y,且xy=1,求证:(x2+y2/x-y)≥2根号2
已知x2+y2=20,x2+xy-2y2=2(x+2y),求x+y的值
已知x-y+1,X2+Y2=25 求(x+y)2和x2-xy+y2的值
已知2x=3y,求xy/(x2+y2)-y2/(x2-y2)的值
已知X2-2x+y2+6y+10=0,求(x2-2xy)/(xy+y2)的值
已知x,y∈R,比较x2+y2与2(2x-y)-5的大小
已知x,y∈R,且1≤x2+y2≤2,z=x2+xy+y2,则z的取值范围是
已知x2+y2-10x-6y+34=0,求(x-y/x+y)2÷x2-y2/xy×x2+2xy+y2/x2-xy 的值.
已知:x=3,y=-5,x2-2xy+y2/x2-y2的值是
已知x,y均为正数,且x>y,求证:2x+1/(x2-2xy+y2)>=2y+3
已知x2-2xy=3y2且x,y为非零实数 求:(1)2x+y/x-2y (2)2x2-3y2+5xy/x2+xy+y2