eq - equation.
y - default unknown y(x).
x - variable x.
n - the nth order of equation.

Description

For first order differential equation, there are 3 ways to input derivative:
1. y'
2. y(1,x)
3. ds(y) or ds(y,x)
where ds( ) is a derivative holder.

For second order differential equation, there are 3 ways to input derivative:
1. y''
2. y(2,x)
3. ds(y,x,2)
where y'' is two sinlge quote sign, instead one double quote sign.

For fractional order differential equation, there are 2 ways to input derivative:
1. y(0.5,x)
2. ds(y,x,0.5)

Solution can be tested by test( ). If test(solution,eq) give 0, solution satisfy the equation.