Suppose a function f is defined as follows: You start with a real number x and add 3. Then you square the resulting number. Finally you multiply the resulting number by 4. Which of the following formulas represents f(x)?
a. f(x) = 4(x2 + 3)
b. f(x) = 4x2 + 3
c. f(x) = (4x + 3)2
d. f(x) = 4(x + 3)2