Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Picture a point in the first quadrant (+,+) doesn't matter where exactly

1. If the product of the X intercepts is positive then they both cross the X axis on the same side of the Y axis (ie, the intercepts are either both positive or both negative). Both lines could cross on the positive side and have opposite slopes (or the same type of slope).

INSUFFICIENT

2. this means the lines cross the Y axis on different sides of the X axis. They could cross on opposite sides with the same sign slope (just different degrees of slope) or different signed slopes.

INSUFFICENT

now taken TOGETHER. They have to cross the X axis on the positive side, but cross the Y axis on different sides of the X axis. For this to be possible they MUST have different signed slopes. One negative and one positive.

Answer is C.

I know this is maybe the worst explanation ever given. I didn't write anything down or chart it out, I just pictured the situation and went from there. Try sketching it out and seeing for yourself.