Solution:
Let x be a positive real number. By AM-GM we have 41+x+x+x≥x43, or equivalently 1+3x≥4x43. Using this inequality we obtain:
(3a2+1)2≥16a3 and 2(1+b3)2≥32b−23
Moreover, by inequality of arithmetic and geometric means we have
f(a,b)=(3a2+1)2+2(1+b3)2≥16a3+32b−23=16(a3+b−23+b−23)≥48ba
Therefore, we obtain
f(a,b)f(b,c)f(c,a)≥48⋅ba⋅48⋅cb⋅48⋅ac=483
Equality holds only when a=b=c=1.