GRE

题目

GRE
In the xy-plane,line k is a line that does not pass through the origin.Which of the following statements individually provide(s) sufficient additional information to determine whether the slope of line k is negative?Indicate all such statements.
A.The x-intercept of line k is twice the y-intercept of line k.
B.The product of the x-intercept and the y-intercept of line k is positive.
C.Line k passes through the points (a,b) and (r,s),where (a – r)(b – s) < 0.

答案

如果直线k不经过原点,那么斜线方程为y=kx+b(b不等于0),k就是斜率.题目中问斜率为负的充分条件首先当然是斜率存在,即斜线k不与X轴垂直.A 选项如果他说了X和Y上的截距那就说明截距是存在的,那么就不存在斜线平行于X轴...