t x 1 x 3 t 1 3 t 3 t3 2 t3 1 dx dt dx dt dt x 1 t t x t 1 2 1 t 3 3 2 t t3 3 dt t t3 ln t C t 3 2 x 1 3 3 2 x 1 3 x 1 ln x 1 C 3 2