已知|x|≤1,|y|≤1,求证：|x+y/1+xy|≤1.已知|x|≤1,|y|≤1,求证：|x+y/1+xy|≤1.求证：|（x+y）/（1+xy）|≤1.

已知|x|≤1,|y|≤1,求证：|x+y/1+xy|≤1.已知|x|≤1,|y|≤1,求证：|x+y/1+xy|≤1.求证：|（x+y）/（1+xy）|≤1. 已知x^2-2xy+y^2+x+y+1=0求证:1/3≤y/x≤3 已知x>0,求证：7-x-9/x≤1 已知|x|≤1,|y|≤1,求证|x+y/1+xy|≤1.已知|x|≤1,|y|≤1,求证|x+y/1+xy|≤1 | |代表绝对值 已知x²+y²≤1,求证:|x²+2xy-y²|≤根号2 已知x>y>0,求证x+1/(x-y)x>=3 已知x,y∈R,求证:x+y+1≥x+y+xy 已知x,y∈R,求证:x^2+y^2≥xy+x+y-1 已知x,y,z∈R,求证:x^2+y^2>=xy+x+y-1 已知x,y∈R,求证:x-xy+y≥x+y-1 已知x>0y>01/x+9/y=1,求证：x+y>=16.快 已知x,y属于R 满足（x^2+y^+2)(x^2+y^2-1)-18≤0 求证 xy≤2 已知x,y∈R,满足（x²+y²+2)(x²+y²-1)-18≤0.求证：xy≤2 已知x,y,z∈R,若x^4+y^4+z^4=1,求证x^2+y^2+z^2≤根号3 已知|sinx-cosx|≤|x-y|,当x＞0时,求证：1/x+1＜ln(1+1/x)＜1/x 已知a,b∈R+,且x+y=1,求证:xy≤1/4 已知非负实数x,y,z满足x+y+z=3 (2),求证x^2/(1+x^4)+y^2/(1+y^4)+z^2/(1+z^4)≤1/(1+x)+1/(1+y)+1/(1+z) f(x+y)+f(x-y)=2f(x)g(x)求证g(y)≤1