If -2x > 3y, is x negative...

by **doitupright** Sat Sep 13, 2008 9:56 pm

If -2x > 3y, is x negative?

1) y > 0

2) 2x + 5y -20 = 0

Correct answer is D

My answer was A, as I understand why 1 is sufficient, but don't see how 2 is also sufficient. Please help! Thanks!!!

by **Khalid** Sun Sep 14, 2008 11:37 pm

2x+5y= 20
Or, y= (20-2x)/5

-2x>3y
Substiture for y
-10x>60-6x
-4x>60

The only way this would be possible is if x is negetive

Hence 2 is sufficient

by **RonPurewal** Thu Oct 09, 2008 7:50 am

Khalid Wrote:2x+5y= 20
Or, y= (20-2x)/5

-2x>3y
Substiture for y
-10x>60-6x
-4x>60

The only way this would be possible is if x is negetive

Hence 2 is sufficient

you got it.

notice the takeaway here:
TAKEAWAY: if you have a simultaneous equation and inequality, then solve the equation and then substitute it into the inequality.