demoskopico
01-23-2008, 01:18 AM
If x/y >2, is 3x+2y<18?
1. x-y is less than 2
2. y-x is less than 2
i solved this ds in this way:
if y>0 then x>2y
if y<0 then x<-2y
1. consider the case in which y>0
x<y+2
-x<-2y
thus y<2 and x<4 ans our inequality is true in all cases
case y<0:
x<-2y
x<2+y
3y<-2, thus y<-2/3 and x<4/3
thus 1. seems suff
2.let's try with y>0
we get x>-4 and y>-2 ...so we don't know if our ineq. is verified...insuff
OA is A.
I spend too much time in solving this way. is there any other quicker method?
thanks a lot
1. x-y is less than 2
2. y-x is less than 2
i solved this ds in this way:
if y>0 then x>2y
if y<0 then x<-2y
1. consider the case in which y>0
x<y+2
-x<-2y
thus y<2 and x<4 ans our inequality is true in all cases
case y<0:
x<-2y
x<2+y
3y<-2, thus y<-2/3 and x<4/3
thus 1. seems suff
2.let's try with y>0
we get x>-4 and y>-2 ...so we don't know if our ineq. is verified...insuff
OA is A.
I spend too much time in solving this way. is there any other quicker method?
thanks a lot