# Assumptions for simplifying a long equation

I'm having trouble combining assumptions with the execution of Simplify in a long equation. The idea is to separate imaginary and real parts of a complex equation. Therefore I am trying to assume the variables as reals.

Simplify[-Re[(a+I b) (2-c-d-I e-I f)],
{a ∈ Reals, b ∈ Reals, c ∈ Reals, d ∈ Reals, e ∈ Reals, f ∈ Reals}]


But the output is just ignoring the assumptions. How should I implement it?

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Did tried builin command ComplexExpand[] – Junho Lee Jul 10 '14 at 12:07
eq = -Re[(a + I b) (2 - c - d - I e - I f)]; ComplexExpand[eq] – Junho Lee Jul 10 '14 at 12:07
When you need to specify that multiple variables are Reals (or other types) they can be grouped together. Element[{a, b, c, d, e, f}, Reals] or (a | b | c | d | e | f) ∈ Reals – Bob Hanlon Jul 10 '14 at 13:18