This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
  d2 y / d x2  =   - x2 y
Bring y to LHS and x to RHS:        d2 y  /  y      =   - x2  d x2 
Integrate on both sides: wrt y on LHS and x on RHS. 
dx2 is dx * dx and d2y is dy * dy. 

      ln y  dy  =  - 1/3  x3   dx

Integrate again:     y ln y – y  = - 1/12  x4