Added December 20, 2018.
Example 27, Taken from https://www.mapleprimes.com/posts/209970-Exact-Solutions-For-PDE-And-Boundary--Initial-Conditions-2018
Solve for \(w(x_1,x_2,x_3,t)\) \[ \frac {\partial w^2}{\partial t^2} = \frac {\partial w^2}{\partial x_1 x_2} + \frac {\partial w^2}{\partial x_1 x_3} + \frac {\partial w^2}{\partial x_3^2} - \frac {\partial w^2}{\partial x_2 x_3} \] With initial condition \begin {align*} w(x_1,x_2,x_3,t_0) &= x_1^3 x_2^2 + x_3 \\ \frac {\partial w}{\partial t}(x_1,x_2,x_3,t_0) &= -x_2 x_3 + x_1 \end {align*}
Mathematica ✓
ClearAll["Global`*"]; pde = D[w[x1, x2, x3, t], {t, 2}] == D[w[x1, x2, x3, t], x1, x2] + D[w[x1, x2, x3, t], x1, x3] + D[w[x1, x2, x3, t], {x3, 2}] - D[w[x1, x2, x3, t], x2, x3]; ic = {w[x1, x2, x3, t0] == x1^3*x2^2 + x3, Derivative[0, 0, 0, 1][w][x1, x2, x3, t0] == -(x2*x3) + x1}; sol = AbsoluteTiming[TimeConstrained[DSolve[{pde, ic}, w[x1, x2, x3, t], {x1, x2, x3, t}], 60*10]];
\[\left \{\left \{w(\text {x1},\text {x2},\text {x3},t)\to t^2 \left (3 \text {t0}^2 \text {x1}-\frac {\text {t0}}{2}+3 \text {x1}^2 \text {x2}\right )+t^3 \left (\frac {1}{6}-2 \text {t0} \text {x1}\right )+\frac {t^4 \text {x1}}{2}+t \left (-2 \text {t0}^3 \text {x1}+\frac {\text {t0}^2}{2}-6 \text {t0} \text {x1}^2 \text {x2}+\text {x1}-\text {x2} \text {x3}\right )+3 \text {t0}^2 \text {x1}^2 \text {x2}+\frac {\text {t0}^4 \text {x1}}{2}-\frac {\text {t0}^3}{6}-\text {t0} \text {x1}+\text {t0} \text {x2} \text {x3}+\text {x1}^3 \text {x2}^2+\text {x3}\right \}\right \}\]
Maple ✓
restart; pde := diff(w(x1, x2, x3, t), t$2)= diff(w(x1,x2,x3,t),x1,x2)+diff(w(x1,x2,x3,t),x1,x3)+diff(w(x1,x2,x3,t),x3$2)-diff(w(x1,x2,x3,t),x2,x3); ic := w(x1, x2, x3, t0) = x1^3*x2^2+x3, eval( diff( w(x1,x2,x3,t),t),t=t0)=-x2*x3+x1; cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve([pde, ic],w(x1,x2,x3,t))),output='realtime'));
\[w \left ( {\it x1},{\it x2},{\it x3},t \right ) ={\frac {{{\it t0}}^{4}{\it x1}}{2}}+{\frac { \left ( -12\,{\it x1}\,t-1 \right ) {{\it t0}}^{3}}{6}}+{\frac { \left ( 18\,{\it x1}\,{t}^{2}+18\,{{\it x1}}^{2}{\it x2}+3\,t \right ) {{\it t0}}^{2}}{6}}+{\frac { \left ( -36\,t{{\it x1}}^{2}{\it x2}+ \left ( -12\,{t}^{3}-6 \right ) {\it x1}-3\,{t}^{2}+6\,{\it x2}\,{\it x3} \right ) {\it t0}}{6}}+{{\it x1}}^{3}{{\it x2}}^{2}+3\,{t}^{2}{{\it x1}}^{2}{\it x2}+{\frac { \left ( 3\,{t}^{4}+6\,t \right ) {\it x1}}{6}}+{\frac {{t}^{3}}{6}}-{\it x2}\,{\it x3}\,t+{\it x3}\]
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