Graphing inequalities

[MoooShuuu]

Advertisement - Members don't see this ad

Can someone clarify this for me?

How would you go about finding the graph for any of these?

x(y-2x)>/= 0
x(y-2x)</=O
x(y+1/2x)>/= O

 

[MoooShuuu]

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??

 

[Marmar tala]

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

 

[MoooShuuu]

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.

 

[Streetwolf]

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.