Hello from MrBillDoesMath!
Answer: h <> 10 and h <> 2 ( <> means not equal)
Discussion :
The domain restrictions are where the denominator is 0. In this problem that occurs when
h^2 -12h + 20 = 0.
Factoring this equation gives
(h-10) (h-2) = 0
So the values h = 10 and h =2 are NOT in the domain of this function,
Regards, MrB