Yes, that is a very good way to view it. For people who want to make absolutely sure, or for more complicated problems, one would have to actually plug it in and try it out.

1. f(x) = 1-x

f(1-x)=1-(1-x)=x

No

2. f(x) = 1 - x^2

f(1-x)=1-(1-x)^2

No

3. f(x) = x^2 - (1 - x) ^2

f(1-x)=(1-x)^2-x^2=-f(x)

No

4. f(x) = x^2 ( 1 - x) ^2

f(1-x)=(1-x)^2x^2=f(x)

Yes

5. f(x) = x / (1-x)

f(1-x)=(1-x)/x

No

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