已知a>0,b>0,a+b=1,求證(a+1/a)(b+1/b)大於等於25/4

已知a>0,b>0,a+b=1,求證(a+1/a)(b+1/b)大於等於25/4

a+b≥2√ab
ab≤1/4
(a+1/a)(b+1/b)
=(a^2+1)/a*(b^2+1)/b
=[a^2b^2+(1-2ab)+1]/ab
=[(ab-1)^2+1]/ab
(ab-1)^2+1≥25/16
0