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题库 / Prep2007E1-DS-213
If a and b are positive numbers, what are the coordinates of the midpoint of line segment CD in the xy-plane?
(1) The coordinates of C are (a, 1 - b).
(2) The coordinates of D are (1 - a, b).
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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根据坐标中点公式直接求出CD中点为(1/2,1/2)
这题想的太复杂了，不必纠结a,b具体取值是否大于1！
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