Number Plane Question. (1 Viewer)

[frenzal_dude]

How would you graph this:

4x is less than or same as 15 which is less than or same as -9x

Therefore x is lessthan or the same as 3 3/4 and x is less than or same as -5/3.

For some reason, the answers show a single line showing only x is less than or the same as -5/3, how come?

 

[frenzal_dude]

4x<=15<=-9x
x<=15/4, x>=-5/3

isn't it x <=-5/3 not x >=-5/3 ?? because when u divide both sides by a negative number u flip the sign.

 

[klaw]

yeah I forgot to switch the signs in that one... it's the answer in the book because it has to satisfy both domains

 

[frenzal_dude]

but the answer doesnt satisfy both domains, because the line doesnt show it being equal to 3 3/4??

also in numberlines do u only have one line on the graph? like in my one i did 2 lines, can u ever do that?

 

[klaw]

-5/3<=x<=15/4 doesn't satisfy x<=-5/3.

 

[word.]

This is a number line, not a number plane...

4x <= 15 <= -9x

We are looking for values of x which satisfy both:
4x <= 15 and 15 <= -9x

x <= 15/4 and x <= -5/3

We eliminate the values -5/3 < x <= 15/4 because they don't satisfy x <= -5/3.

You can have two lines on a number line if the arrowheads point in opposite directions:
eg. x² > 25: x > 5 and x < -5