Hi, write some lines of Wolfram code to find a solution to an integral using the substitution method:

f[x_] := Power[x, 3]*Power[2 - Power[x, 2], 12]; f[x]
s1 = Integrate[f[x]*Dt[x] /. {x -> Sqrt[2 - u]} /. {2 - x^2 -> u} /. {-2 x*Dt[x] ->1} /. {Dt[u] -> 1}, u]
s2 = Expand[s1]
s3 = s2 /. {u -> 2 - Power[x, 2]}

Try to write a wolfram function to solve integrals using the method (wrong code):

IntSubs[f_, x_, u_] := Integrate[f*Dt[x] /. {x -> u}, u]

Could someone help to write a function to calculate integrals by substitution? Thanks!