In the xy-plane, the origin O is the midpoint of line segment PQ. If the coordinates of P are (r,s), what are the coordinates of Q ?
A. (r,s)
B. (s,–r)
C. (–s,–r)
D. (–r,s)
E. (–r,–s)
Answer: E
Source: official guide
In the xy-plane, the origin O is the midpoint of line segment PQ. If the coordinates of P are (r,s), what are the coordi
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Let's sketch a line segment with midpoint at the origin and an endpoint at (r, s)BTGModeratorVI wrote: ↑Thu Dec 03, 2020 2:45 pmIn the xy-plane, the origin O is the midpoint of line segment PQ. If the coordinates of P are (r,s), what are the coordinates of Q ?
A. (r,s)
B. (s,–r)
C. (–s,–r)
D. (–r,s)
E. (–r,–s)
Answer: E
Source: official guide
We can now travel the SAME DISTANCES (from the origin) to ensure that the origin is the midpoint.
From here, we can see that (-r, -s) are the coordinates of the other point.
Answer: E
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Solution:BTGModeratorVI wrote: ↑Thu Dec 03, 2020 2:45 pmIn the xy-plane, the origin O is the midpoint of line segment PQ. If the coordinates of P are (r,s), what are the coordinates of Q ?
A. (r,s)
B. (s,–r)
C. (–s,–r)
D. (–r,s)
E. (–r,–s)
Answer: E
Source: official guide
We use the midpoint formula: (x_1 + x_2)/2 = x-coordinate of the midpoint and (y_1 + y_2)/2 = y-coordinate of the midpoint.
We know that the coordinates of P are (r, s), and we can let the coordinates of Q be (x, y). Since the origin (0, 0) is the midpoint of PQ, we have:
(r + x)/2 = 0 and (s + y)/2 = 0
Multiplying each equation by 2, we have:
r + x = 0 and s + y = 0
x = -r and y = -s
Thus, the coordinates of Q are (-r, -s).
Answer: E
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