This seems so easy, but I can't figure it out.

Determine whether the function is one-to-one

f(x) = x^4 + 5

is it asking that the range and the domain are unique? Meaning for every x there is a unique f(x), and for every finverse(x) you get back the original x and no more?

f(-1) = 6
f(1) = 6

clearly not one to one
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or more formally

f(a) = f(b)
a^4 + 5 = b^4 + 5

a^4 = b^4

a = +/- b

again, clearly not 1 to 1

lol I swear I tried that...thanks as always man!

you got the answer but let me give you a hint:
for polynomial functions having as domain the whole real line
those of an even degree are never one-to-one

yeah anytime you beat on one of these even power ones, you'll always encounter the problem above, a +/- will creep in, ruining everything