1.  dsolve===>> to solve linear differential equation, just write the equation in inverted comma and initial condition also in inverted comma. to assign value of answer you can use variable name in big bracket in left hand side.
  2. solve==>>to solve any number of equation
  3. vdp1==> is vanderpol oscillator with mu=1. you can directly use this to solve
  4. to solve nonlinear differential equation you can use ode45, see the syntax