Hi guys I'm new here and I thought that maybe you could help me with this problem. I don't quite understand the notation and what the thing is meaning.

Prove the following:

(D-a)(D-b){f(x)e^(λx)} = e^(λx)(D+λ-a)(D+λ-b)f(x)

(D^2+aD+b){f(x)e^(λx)} = e^(λx){(D+λ)^2+a(D+λ)+b}f(x)

I just know that

But what does the curly parenthesis notation mean?

Any ideas?