prep-ds-16

Lines n and p lie in the xy-plane. Is the slope of line n less than the slope of line p?

1,lines n and p intersect at the point (5,1)

2, the y-intercept of line n is greater than the y-intercept of line p.

y-intercept是有正负之分的，那么要讨论的情况应该很多，怎么可以确定选C呢？

呵呵，设lines n,p与y的交点为（0,n）(0,p)， 又知两线交点为（5,1）then

the slope of line n is: (1-n)/5

the slope of line p is: (1-p)/5

because n is greater than p,so (1-n)<(1-p)=>the slope of line n is less than that of line p.

因为n>p

举反例：n＝－5； p＝3  1－n>1-p ＝》the slope of line n is greater than of line p.