Graphing inequalities

This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.
Wouldn't graphing the first equation and second equation basically be the same thing for an equality? This is a kaplan problem in the DAT Review note book (pg 92), and the solution says for the first equation:

A) x(y-2x)>= 0

X>=0 y>=2x and the opposite is true, x<=0 y<= 2x

for B) x(y-2x)<=O the solution is:

X<=0 y<=2x and the opposite is true, x>=0 y>= 2x . Why is the answer A and not B??
 
Last edited:
because A and B have two different inequality, expression in A is greater than or equal zero and in B is less than or equal zero.
so in B, either ( X<= 0 and y>=2X ) OR (X>=0 and Y<=2X) is true.
let say you have two numbers multiplied together and the answer is negative , then you would say it must be that one number is positive(>=0) and one is negative(<=0) in order to get a negative number out of the multiplication
 
I'm still not seeing it...
X>=0 y>=2x and the opposite is true, x<=0 y<= 2x

X<=0 y<=2x and the opposite is true, x>=0 y>= 2x

So aren't these the same basic equations? 😕 I have no math sense.
 
I'm still not seeing it...
X>=0 y>=2x and the opposite is true, x<=0 y<= 2x

X<=0 y<=2x and the opposite is true, x>=0 y>= 2x

So aren't these the same basic equations? 😕 I have no math sense.
You need x >= 0 paired up with y <= 2x for B otherwise you'll get >= 0 when you multiply them.

If x and y-2x are both positive then you'll get a positive answer so one of them has to be negative and the other positive. Also you'd have x <= 0 paired up with y >= 2x.
 

Similar threads

D
  • Question Question
Replies
2
Views
1K
D
  • Question Question
Replies
4
Views
670
Replies
0
Views
500
D
  • Question Question
Replies
3
Views
787
Top