HomeWork 10 problem 4

I am having trouble with HW problem 4
What is the correct way to express a rejection region as opposed to a confidence interval?
Thanks

Rejection regions are written in parentheses and include the use of -infinity and infinity. Confidence intervals are written in brackets.
For example if you are doing the webwork problem you would format it as:
(-infty,x)U(x,infty)
and it would look like:
(−∞,x)∪(x,∞).
I hoped this help!