1. The problem states the candidate pixel update formula: $$p_{k+1} = p_k + 2\Delta y - 2\Delta x$$ given that $$y_{k+1} - y_k = 1$$. 2. This formula is typically used in line drawing algorithms like Bresenham's, where $p_k$ is the decision parameter at step $k$, and $\Delta x$, $\Delta y$ are the differences in the $x$ and $y$ coordinates between the start and end points. 3. The condition $$y_{k+1} - y_k = 1$$ means the $y$ coordinate increments by 1 at the next step. 4. The formula updates the decision parameter by adding $$2\Delta y - 2\Delta x$$ to the current parameter $p_k$. 5. This helps decide the next pixel to plot when the line moves vertically by one pixel. 6. To use this formula, you start with an initial $p_0$ and iteratively compute $p_{k+1}$ to determine pixel positions. Final answer: The candidate pixel update formula under the condition $$y_{k+1} - y_k = 1$$ is $$p_{k+1} = p_k + 2\Delta y - 2\Delta x$$.