The graph of f (x) = x2 is shifted 3 units to the left to obtain the graph of g (x). Which of the following equations best describes g (x) ?

When you add a positive value to the argument of a function, its graph shifts to the left, the same number of units added to the argument.

This is, the graph of f (x+a) is the graph of the function f (x) shifted a units to the left.

Then, g (x) is f (x+3) = (x+3) ^2