xy-plane

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 56
Joined: Sat May 24, 2008 5:18 pm
Thanked: 1 times

xy-plane

by anwarma » Thu Jun 12, 2008 3:41 pm
In the xy-plane, line k has a positive slope and x-intercept of 4. If the area of the triangle formed by the line k and the two axes is 12, what is the y-intercept of line k?

(A) -6
(B) -4
(C) -3
(D) 3
(E) 6

What i want to know how come it is -6 when I calculated it to +6. Can someone enlighten me?
AA
Source: — Problem Solving |

Master | Next Rank: 500 Posts
Posts: 178
Joined: Wed May 14, 2008 3:51 pm
Thanked: 16 times
Followed by:1 members
GMAT Score:99%+

by egybs » Thu Jun 12, 2008 4:14 pm
it's a positive slope... so we know that the y intercept is going to be negative if the x intercept is 4. Just draw it out if you can't see it.

If there were points (0,6) and (4,0), we'd have a negative slope. with (0,-6) and (4,0) we have a positive slope.