To shift the function \( f(x) = (x + 1)^3 \) to the left by 3 units, you need to replace \( x \) with \( x + 3 \) in the equation.
So, the new function will be:
\[ f(x) = ((x + 3) + 1)^3 \]
This simplifies to:
\[ f(x) = (x + 4)^3 \]
Therefore, the final answer is:
\[ f(x) = (x + 4)^3 \]
If you want to express it in the form \( f(x) = (x + __)^3 + __ \), it would be:
\[ f(x) = (x + 4)^3 + 0 \]
So, \( f(x) = (x + 4)^3 + 0 \).