To find the function \( g(x) \) based on the rule "reflect across the x-axis" from the function \( f(x) = -2x + 1 \), we take the function \( f(x) \) and multiply it by -1.
Reflecting the function across the x-axis means that:
\[ g(x) = -f(x) \]
So we calculate:
\[ g(x) = -(-2x + 1) = 2x - 1 \]
Now, let's look at the provided options:
- \( g(x) = 2x - 1 \)
- \( g(x) = -2x - 1 \)
- \( g(x) = 2x + 1 \)
- \( g(x) = - (2x - 1) \)
The correct function after reflecting \( f(x) = -2x + 1 \) across the x-axis is \( g(x) = 2x - 1 \).
Therefore, the answer is:
g(x) = 2x - 1.