[shengsheng]

clear
syms x;
Dsolve('D2y-3*Dy+2*y=x','y(0)=0','Dy(0)=0','x')
f =ans;
subs(f,x,0.5)


ans =

1/2*x+3/4+1/4*exp(2*x)-exp(x)



ans =

0.0308