已知抛物线$y=-x^{2}+bx+3$经过直线$y=-x+3$与坐标轴的两个交点$A$，$B$，此抛物线与$x$轴的另一个交点为$C$，抛物线的顶点为$D$，若点$M$为抛物线上一动点（不与点$B$重合），使$\triangle ACM$与$\triangle ABC$的面积相等，求点$M$的坐标。---**Chart Description:** * **Type:** Cartesian Coordinate System with graphs of a parabola and a straight line. * **Coordinate Axes:** Standard horizontal X-axis and vertical Y-axis intersecting at the origin O. The positive direction of the X-axis is to the right, and the positive direction of the Y-axis is upwards. * **Graphs:** * **Parabola:** A curve opening downwards. It intersects the X-axis at two points, C (on the negative X-axis) and A (on the positive X-axis). It intersects the Y-axis at point B (on the positive Y-axis). The highest point of the parabola, the vertex, is labeled D and is located in the first quadrant (above the X-axis and to the right of the Y-axis). * **Straight Line:** A line segment passing through points A (on the positive X-axis) and B (on the positive Y-axis). The line has a negative slope. * **Labeled Points:** * O: Origin (0,0). * A: A point on the positive X-axis. It is an x-intercept of the parabola and the straight line. * B: A point on the positive Y-axis. It is a y-intercept of the parabola and the straight line. * C: A point on the negative X-axis. It is another x-intercept of the parabola. * D: The vertex of the parabola, located in the first quadrant.