^(3n-1)/a^(2n-1)×c÷b^(3n-2)/a^2n
=b^(3n-1)/a^(2n-1)×c×a^2n/b^(3n-2)
=bb^(3n-2)/a^(2n-1)×c×aa^(2n-1)/b^(3n-2)
=abc