Variables in Maple are denoted by sequences of letters, digits, and underscores, not begining with a digit. For example,

x, Y , z, boundary_condition, ODE2, \_aA
are all legimtimate variables, but 3b is not.

Not all combinations are allowed as some names are already used in Maple. For instance, Greek letters are all in Maple alphabet:

    Greek letters

  Word   Symbol   Word   Symbol   Word   Symbol   Word   Symbol
  alpha         α   beta         β   gamma         γ   delta         δ
  epsilon         ε   zeta         ζ   eta         η   theta         θ
  iota         ι   kappa         κ    lambda          λ   mu         μ
  nu         ν   xi         ξ    omicron          ο   pi         π
  rho         ρ   sigma         σ    tau          τ   upsilon         υ
  phi          ϕ   chi         χ    psi          ψ   omega         ω
Also, the symbol Pi and I are reserved for the constant π = 3.1415926… and the unit vector in the positive vertical direction on the complex plane &‌#8450;. On the other hand, letters e and i are not used by Maple. One can define the base of the natural logarithm as e = exp(1), which is 2.718281828459… .

All the standard mathematical functions have pre-defined names in Maple. The following reserved words are not accepted as valid names in maple.

Maple reserved names
  and     ;by    do      done    elif      RETURN   else      end
  fi     for    from      break    if      in   intersect      local
  minus     next    mod      not    od      option   options      or
  proc      quit    read      save    stop      then   to      union
and some others (such as while). (a*b)/c+13*d \[ {\frac {ab}{c}}+13\,d \]
Two n-by-n matrices A and B are called similar if there exists an invertible n-by-n matrix S such that
Theorem: If λ is an eigenvalue of a square matrix A, then its algebraic multiplicity is at least as large as its geometric multiplicity.    ▣
Let x1, x2, … , xr be all of the linearly independent eigenvectors associated to λ, so that λ has geometric multiplicity r. Let xr+1, xr+2, … , xn complete this list to a basis for ℜn, and let S be the n×n matrix whose columns are all these vectors xs, s = 1, 2, … , n. As usual, consider the product of two matrices AS. Because the first r columns of S are eigenvectors, we have
\[ {\bf A\,S} = \begin{bmatrix} \vdots & \vdots&& \vdots & \vdots&& \vdots \\ \lambda{\bf x}_1 & \lambda{\bf x}_2 & \cdots & \lambda{\bf x}_r & ?& \cdots & ? \\ \vdots & \vdots&& \vdots & \vdots&& \vdots \end{bmatrix} . \]
Now multiply out S-1AS. Matrix S is invertible because its columns are a basis for ℜn. We get that the first r columns of S-1AS are diagonal with &lambda's on the diagonal, but that the rest of the columns are indeterminable. Now S-1AS has the same characteristic polynomial as A. Indeed,
\[ \det \left( {\bf S}^{-1} {\bf AS} - \lambda\,{\bf I} \right) = \det \left( {\bf S}^{-1} {\bf AS} - {\bf S}^{-1} \lambda\,{\bf I}{\bf S} \right) = \det \left( {\bf S}^{-1} \left( {\bf A} - \lambda\,{\bf I} \right) {\bf S} \right) = \det \left( {\bf S}^{-1} \right) \det \left( {\bf A} - \lambda\,{\bf I} \right) \det \det \left( {\bf S} \right) = \det \left( {\bf A} - \lambda\,{\bf I} \right) \]
because the determinants of S and S-1 cancel. So the characteristic polynomials of A and S-1AS are the same. But since the first few columns of S-1AS has a factor of at least (x - λ)r, so the algebraic multiplicity is at least as large as the geometric.    ◂