1. The problem statement, all variables and given/known data It is possibly not a homework problem.However,to do a homework problem,I require this: Boas writes the effect of Ladder operators on y_n that satisfies y"_n-x^2y_n=-(2n+1)y_n,n=0,1,2,3... (D-x)(D+x)y_n=-2ny_n (D+x)(D-x)y_n=-2(n+1)y_n Then,she proved y_(m-1)=(D+x)y_m and the other raising operator eqn. So far there is no problem... Now she says,if n=0,we find a solution of (D-x)(D+x)y_n=-2ny_n by requiring (D+x)y_0=0 My question is if n=0,we have (D-x)(D+x)y_0=0. Does that mean (D+x)y_0=0 necessarily? 2. Relevant equations 3. The attempt at a solution treating (d+x)y_0=t,I saw that we have (D-x)t=0 or,t=c exp[x^2/2] So,they are treating c=0?...why? I am toatlly confused.Please help.