How Do Find The Complement of a Function (Digital Logic)?

Question

I'm in VLSI and I think I've forgotten how to do this..but I may have to on a test (designing Compound Gates using transistors..). So for example: Y = AB + C+D

Would the complement be

A(complement) + B(complement) *C(complement)*D(complement)

I know it's probably simple, but it's been a really long time since I've taken digital logic. Thanks

Answer 1

Y'=(AB + C + D)' Using Demorgan's theorem,
Y'=(AB)' * C' * D' Again using Demorgan's theorem,
Y'= (A' + B') * C' * D'
That would be my answer.

Edit
I think it can be simplified more actually
Y'=A'C'D' + B'C'D'
That would be my final answer.

Answer 2

Make a truth table for Y, then invert it, and find out which terms make Y'

I get:
Y' = C'D' * (A'B' + A'B + AB')

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