1/x+1/y=(1/x+1/y)*(2x+y)=3+2x/y+y/x≥3+2√2当且仅当x=(2-√2)/2时取等号。1/x+1/y最小值为3+2√2
2x+y=1≥2*2x*y→xy≤1/4→1/xy≥41/x+1/y≥2*1/xy因为1/xy≥4所以1/x+1/y≥81/x+1/y最小为8
