ANSWER
f(-4) = 20
EXPLANATION
To find f(-4) we just have to replace x by -4 in function f(x):
[tex]f(-4)=(-4)^2+4[/tex]First solve the exponents. Remember that if the exponent is even and the result is always positive, either the base is positive or negative:
[tex]f(-4)=16+4=20[/tex]