Final answer:
To find the coordinates of point B in the first quadrant, calculate the distance between points C and D, and add it to point A's x-coordinate. The coordinates of point B are (7, 1).
Step-by-step explanation:
To find the coordinates of point B in the quadrilateral ABCD, we take into account that segments AB and DC are equal in length and both are horizontal. Since we have the coordinates of points A (1, 1), C (4.5, 4), and D (-1.5,4), we can deduce the length of segment DC (or AB) by calculating the distance between points C and D, which are both on the same horizontal level (y-coordinate of 4).
The distance between C and D is the absolute difference in their x-coordinates: |4.5 - (-1.5)| = 6.0 units. Since AB is horizontal and of the same length, we add this distance to the x-coordinate of A to find the x-coordinate of B. The y-coordinate of B would be the same as that of A, as segment AB is horizontal.
So the x-coordinate of B is 1 + 6.0 = 7.0. Therefore, the coordinates of point B are (7, 1).