1. Given that f(x) is always a positive value, then which of the following
could be f(x)?
Mark all that apply.
a) f(x) = x5 + x³ + x + 1
b) f(x) = x4 + x² + 1
c) f(x) = x³ + x
d) f(x) = x² + 1
e) f(x) = x² + 5x+1