x,y∈R+求证:(x+y)(x^2+y^2)(x^3+y^3)>=8x^3y^3在线等啊 答对加分！！

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 x,y∈R（高二不等式）x,y∈R,求证｜x-y｜≥|｜x｜-｜y｜| x,y∈R+求证:(x+y)(x^2+y^2)(x^3+y^3)>=8x^3y^3在线等啊 答对加分！！ 已知x,y∈R,求证:x+y+1≥x+y+xy 已知x,y∈R,求证:x-xy+y≥x+y-1 |x|>1,|y|>1,x,y∈R,求证|（x-y）/（1-xy）| x,y∈R.x+y=1 求证(x+1)²+(y+2)²≥25/2x,y∈R.x+y=1 求证(x+2²+(y+2)²≥25/2 若x,t∈{x∈R|x>0},切x+y>2,求证:(1+x)/y 已知x,y∈R*,x+y=1,求证2/x+1/y≥3+2根号2 x,y∈R.x+y=1 求证(x+2²+(y+2)²≥25/2 x,y∈R.x+y=1 求证(x+1)²+(y+2)²≥25/2 若xy∈R+ x+y=2 求证1/x+1/y≥2 若xy∈R+ x+y=2 求证1/x+1/y≥2 已知x,y∈R,求证（x2+y2）2≥xy(x+y)2 假设集合U={(x,y)|x∈R,y∈R },A={(x,y)|2x-y+m>0},B={(x,y)|x+y-n 已知f(x)的定义域为R,对任意x,y∈R,有f(x+y)+f(x-y)=2f(x)f(y),且f(0)≠0.求证：y=f(x)为偶函数 若x.y属于R,且满足（X*X+Y*Y+2）（X*X+Y*Y-1）-18≤0.求证：XY≤2