Gmat Prep: xy plane

[chetanojha]

Please help me to understand the answers

[ketkoag]

here as we know that by both the statements alone we'll not get any thing regarding the y intercept.
now by both the statements combined we have x intercept = -1/3 and slope be 3 times the y intercept.
now slope is y/x and by this we cannot get the value of y intercept as there would be 2 values one for the positive slope and one for the negative slope. so there is not unique value. hence insuff.
hence E is the answer.

[DeepakR]

y=mx+c is the equation of line.

To find y-intercept, x=0 hence y=c. If we know the value of c we are done with the problem.

1. Slope=3 times y-intercept i.e m=3c from which we cannot find c hence A or D is ruled out

2. x-intercept = -1/3 i.e mx+c=0 (since y=0 for x-intercept)
so, m(-1/3) + c = 0 from which we cannot find c

Combining 1 and 2 we cant find hence E.)

-Deepak