To reflect the function \( y = (x + 1)^2 \) across the y-axis, you need to replace \( x \) with \( -x \) in the equation.
Starting with the original function:
\[ y = (x + 1)^2 \]
When reflecting across the y-axis, we replace \( x \) with \( -x \):
\[ y = (-x + 1)^2 \]
This can also be simplified as follows:
\[ y = (1 - x)^2 \]
Thus, the equation of the transformed function, which reflects the original function across the y-axis, is:
\[ y = (1 - x)^2 \]
So the final answer is:
The equation of the transformed function is \( y = (1 - x)^2 \).