2.9 Euler-Poisson-Darboux equation

  2.9.1 \(u_{xx} + u_{yy} + \frac {\beta }{x} u_x = 0\)
  2.9.2 \(u_{xx} - u_{yy} + \frac {\beta }{x} u_x = 0\)
  2.9.3 \(u_{tt} - u_{xx} - \frac {2}{x} u_x = 0\) with \(u(x,0)=0,u_t(x,0)=g(x)\)

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