是不是1/x+1/y?(1/x+1/y)(x+2y)=3*(1/x+1/y)(1/x+1/y)(x+2y)=1+2+2y/x+x/y=3+2y/x+x/y所以1/x+1/y=(3+2y/x+x/y)/3x>0,y>0所以2y/x+x/y>=2√(2y/x*x/y)=2√2当2y/x=x/y时取等号x^2=2y^2x=√2y即y=3/(2+√2),x=3√2/(2...