Final answer:
The formula of the function that is shifted left 2 and stretched vertically by a factor of 3 is f(x) = 3x.
Step-by-step explanation:
The formula of the function that is shifted left 2 and stretched vertically by a factor of 3 can be found by applying the transformations to the parent function.
(a) The parent function is f(x) = 3(x + 2). To shift left 2 units, we need to substitute (x + 2) with (x + 2 - 2) = (x). To stretch vertically by a factor of 3, we need to multiply the function by 3. So, the transformed formula is f(x) = 3x.
Therefore, option (a) (f(x) = 3x) corresponds to the function that is shifted left 2 and stretched vertically by a factor of 3.