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题库 / GMATLA-DS-44
If Line k in the xy-plane has equation y=mx + b, where m and b are constants, what is the slope of k?
(1) k is parallel to the line with equation y=(1-m)x+b +1.
(2) k intersects the line with equation y=2x+3 at the point (2, 7).
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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m=1-m
(2)得出两个推论：线K通过点(2,7)；线k的斜率m不等于2。
1个点没法定义线，也无法确定它的倾斜情况。排除了一条线还有无数条线符合情况，无法确定。
若直线K在xy平面中方程为y=mx+b, 且m与b为常数, 求直线k的斜率?
the slope of line k and the other line are the same since the two lines are parallel, and thus m= 1 - m, and therefore m= 1/2. 平行代表斜率一样