dynamic equation in matlab

how to plot this dynamic equation

[John D'Errico]

Why not start with ODE45?

[Walter Roberson]

You will need to use a numeric algorithm. The symbolic approaches only work for x1(0) = 0, or for a very specific relationship between x1 and its derivative that is difficult to achieve and which is not prescriptive (that is, the symbolic approaches give a formula for recognizing that a propose x1(t) satisfies the requirements, but it would be very difficult to use the formula to construct a solution.)