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Mathematics>Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer.

In the x y-plane, line l passes through the points (a,0) and (0,2a), where a > 1. What is the slope of line l?

(A) -2
(B) -1/2
(C) 2
(D) -2a
(E) 2a

答案和解析

答案：E

解析：

Choice (A) is correct. Given two points on a line, the slope of the line can be found by dividing the change in the y-coordinates between the points by the corresponding change in the x-coordinates. Hence, since line l passes through the points (a,0) and (0,2a), its slope is change in y-coordinates/change in x-coordinates = ((2a)-0)/(0-a) = (2a)/-a = -2.