Problems with matlab symbolic dsolve function

Hi I feel that something is going wrong with matlab dsolve function. Here is simple code:

syms y x
dsolve('9*D2y+y=x*exp(-x^2)')

answer:

x*exp(-x^2) + C2*cos(t/3) + C3*sin(t/3)

Solution does not have the first term. Still, how matlab gives such answer? Any ideas?

Answer 1

[Amit Kumar]

Any ideas?

Answer 2

[Stefan Wehmeier]

The correct syntax is

syms y(x)
dsolve(diff(y, x, x) +y==x*exp(-x^2))

as it declares y as a function of x (and not of t). Alternatively, you can add x as a second argument to your input; but we do not recommend to use character strings.