The question is like ∫x³ dx/1+x⁴

let x⁴ = y

then 4x³ dx = dy

         =>x³ dx = dy/4

Now  1/4∫ dy/(1+y)

        1/4 * log(1+y) + c where c is a constant

put the value of y we get

       1/4 *log(1+x⁴)