Question

设x大于0,y大于0,xy=4.则s=x/根号y+y/根号x取最小值时x的值

Answer 1

设x大于0,y大于0,xy=4.则s=x/√y+y/√x 取最小值时x的值

s=x/√y+y/√x >=2√ (xy/√xy)=2√(√xy)=2*(xy)^(1/4)

xy=4>=2√xy > [(xy)^(1/2)]^2=