Which function Is even?

a. f(x) = √x - 3

b.f(x) = 3√x

c. f(x) = |x| + 4

I keep getting neither even or odd.
HELP PLEASE...

even function :

f(-x) = f(x)
or
there is a reflection in the y-axis

odd function:
f(-x) = -f(x)
or
there is a reflection in the origin.

test each equation with a few values of x