GMAT Prep - coordinate

[singhsa]

In xy plane, line k passes through (1,1) and m through (1, -1). Are lines k and m perpendicular?


a. k and m intersect at (1, -1)
b. k intersects x -axis at (1, 0)

OA - E

[sanju09]

In xy plane, line k passes through (1,1) and m through (1, -1). Are lines k and m perpendicular?


a. k and m intersect at (1, -1)
b. k intersects x -axis at (1, 0)

OA - E

The lines could be parallel or meeting not at right angles, may be, if we are brought here blind to the statements initially.

[1] If k and m intersect at (1, -1), we can only get to the slope of line k only, as we don't get a point on line m other than (1, -1), we cannot get to its slope, and hence the test "Is slope k × slope m = -1?" remains patchy. Insufficient

[2] If k intersects x -axis at (1, 0), then we can only get to the slope of line k only, as we don't get a point on line m other than (1, -1), we cannot get to its slope, and hence the test "Is slope k × slope m = -1?" remains patchy. Insufficient

[spoiler]Due to repeat of repeat

It's E[/spoiler]

[singhsa]

Thanks.