Đáp án:
`\sqrt{a/b}+a/b\sqrt{b/a}`
`=\sqrt{a/b}+\sqrt{a/b}*\sqrt{a/b}*sqrt{b/a}`
`=\sqrt{a/b}+\sqrt{a/b}*\sqrt{a/b*b/a}`(do a,b>0)`
`=\sqrt{a/b}+\sqrt{a/b}*1`
`=2\sqrt{a/b}`
`=(2\sqrt{a})/(\sqrt{b})` (do a,b>0)
`=(2\sqrt{a}*\sqrt{b})/(\sqrt{b}*\sqrt{b})`
`=(2\sqrt{ab})/(b)`
`->` Chọn B.