(1/a+m/b)*(a+b)
=1+b/a+am/b+m
=1+m+(b/a+am/b)
≥1+m+2√[(b/a)*(am/b)]
=1+m+2√m=16
设 m=t^2
则,上式化为
t^2+2t-15=0
(t-3)(t+5)=0
t=3
所以 m=9