试题讲解---Here is the extracted content from the image: **Question 23** **Question Stem:** 23. 定义: 在平面直角坐标系中, 如果一个点的纵坐标是它横坐标的 t 倍 (t 是常数, 且 t≠0), 我们称这个点为“t 倍点”. **(1) Sub-question 1:** 求直线 y = x - 1 上的“-1/2倍点”的坐标. **(2) Sub-question 2:** 已知点 P (x1, y1), Q (x2, y2) 是抛物线 y = ax² + (2b+1)x + c 上的两个“1倍点”, 其中, 实数 a > b > c, a+b+c=0, 设 d=|x1-x2|, 求 d 的取值范围. **(3) Sub-question 3:** 如图, 点 M (m, n) 为抛物线 y = x² - 2x - 1 上一点, 抛物线 y = x² - 2x - 1 上 x ≤ m 部分的图像记为 N1, 将抛物线 y = x² - 2x - 1 上 x > m 部分的图像沿直线 y = n 翻折得到的图像记为 N2, 由图像 N1 与 N2 组成的图像记为 N. 当图像 N 上存在三个“-2倍点” A (x1, y1), B (x2, y2), C (x3, y3), 且满足 x1 < x2 < x3, 2AC=5AB, 写出 m 的值. **Chart/Diagram Description:** * **Type:** Two identical coordinate plane diagrams, each displaying a parabola. * **Main Elements:** * **Coordinate Axes:** In each diagram, there is a horizontal X-axis and a vertical Y-axis. Both axes have arrows indicating their positive directions. The intersection point of the axes is labeled 'O' (origin). * **Graph:** A parabola is drawn in each coordinate system. The parabola opens upwards. Its vertex appears to be in the fourth quadrant. The parabola intersects the X-axis at two distinct points (one positive and one negative) and the Y-axis at a negative point. * **Labels:** The X-axis is labeled 'x', the Y-axis is labeled 'y', and the origin is labeled 'O'. * **Annotation:** Below the two diagrams, there is a text "(备用图)" which translates to "(For reference/spare diagram)".