标题: 麻烦大家帮我看一道data题。多谢了。 [打印本页] 作者: candybobo711 时间: 2011-1-5 08:04 标题: 麻烦大家帮我看一道data题。多谢了。 in the xy-plane, if line k has negative slope and passes through the point (-5, r), is the x-intercept of line k positive？1. the slope of line k is -5 2. r>0作者: sdcar2010 时间: 2011-1-5 09:26
If the line k pass through point (0, b) and (-5, r), then (b-r)/(0-(-5))=k.
So b = 5k+r
1) insufficient. r =1000 or -10000. 2) insufficient. r =1, k=-5. r= 1000, k=-5.
1) and 2). Insufficient. Same as 2).作者: MelissaW 时间: 2011-1-5 21:21
楼上的NN，is the x-intercept of line k positive，应该是和X轴的交点吧作者: sdcar2010 时间: 2011-1-5 21:55
楼上的NN，is the x-intercept of line k positive，应该是和X轴的交点吧
-- by 会员 MelissaW (2011/1/5 21:21:43)
Very true.
If the line k pass through point (0, b) and (-5, r), then (b-r)/(0-(-5))=k.
So b = 5k+r The x-axis intercept a = (-b)/k = -5 -r/k
1) insufficient. r =1000 or -10000. 2) insufficient. r =1000, k=5. r= 1000, k=-5.
1) and 2). Insufficient. r=5, k=-5, a= -4. r= 100, k=-5, a = 15