This is documentation for Mathematica 3, which was
based on an earlier version of the Wolfram Language.
View current documentation (Version 11.2)
 Documentation / Mathematica / The Mathematica Book / Advanced Mathematics / Series, Limits and Residues  /

3.6.6 Solving Equations Involving Power Series

Solving equations involving power series.

  • Here is a power series.
  • In[1]:= y = 1 + Sum[a[i] x^i, {i, 3}] + O[x]^4


  • This gives an equation involving the power series.
  • In[2]:= D[y, x]^2 - y == x


  • LogicalExpand generates a sequence of equations for each power of x.
  • In[3]:= LogicalExpand[ % ]


  • This solves the equations for the coefficients a[i]. You can also feed equations involving power series directly to Solve.
  • In[4]:= Solve[ % ]


    Some equations involving power series can also be solved using the InverseSeries function discussed in Section 3.6.4.