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In the rectangular coordinate system, lines m and n intersect at the origin. Is line m perpendicular to line n?
(1) Line n passes through the point (-a, -a), where a ≠0, and line m has a slope of -1.
(2) The product of the slope of line m and the slope of line n is -1.
We have 2 variables, the slope and the y-intercept for the line. When two lines are orthogonal, the multiple of their slopes is -1.
This problem has 2 lines, thus 4 variables and thus E is likely the answer. When using both 1) and 2), (1) = (2), making D the answer for almost 95%. Since (1) the line go through the origin, the slope of line n is 1 and the slope of line m is -1, satisfying the orthogonality of the two.
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