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#1 2012-11-16 08:40:55
- BarandaMan
- Guest
Small question on inequalities!
Hey!
Hope you all are doing good.
I have
(6/5) > (2/5) - (2/5)z
I get this down to z > 2.
The answer says it should be, z < 2.
Please help me? Thank you!!!!
#2 2012-11-16 08:50:59
- bobbym
- Administrator
Offline
Re: Small question on inequalities!
Hi BarandaMan;
I am getting z > -2.
In mathematics, you don't understand things. You just get used to them.
Probability is the most important concept in modern science, especially as nobody has the slightest notion what it means.
90% of mathematicians do not understand 90% of currently published mathematics.
#3 2012-11-16 08:54:09
- BarandaMan
- Guest
Re: Small question on inequalities!
Really?!
Can you please show me your working?
#4 2012-11-16 08:56:54
- bob bundy
- Moderator
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Re: Small question on inequalities!
hi BarandaMan
x by 5
Add 2z
take 6
divide by 2
I suspect you ran into difficulty because of this
take 2
divide by -2
when you multiply or divide by a negative amount you must reverse the inequality sign
Bob
If you want to explore this rule some more, post back.
hi bobbym, sorry didn't know you were posting too.
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#5 2012-11-16 09:06:04
- BarandaMan
- Guest
Re: Small question on inequalities!
Thank you very very much indeed. The change of the inequality sign is what got me. Thank you for helping me.
This makes sense. With this rule though, I just must remember it, right? Does it exist for a reason? Or is it just one we must remember?
Thanks!!!!
#7 2012-11-16 09:15:14
- bob bundy
- Moderator
Offline
Re: Small question on inequalities!
OK.
Take a look at the diagram
On the right I am trying to show that 3 < 9
When you multiply or divide by -1 it becomes -9 < -3
Make up your own example. When you multiply or divide by a negative it has the effect of reflecting in the 'y axis' so the inequality flips around.
Hope that makes sense.
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#8 2012-11-16 10:20:12
- BarandaMan
- Guest
Re: Small question on inequalities!
Wow, this is incredible. Thank you really. I don't know why people don't get taught stuff like this sometimes, or maybe I forgot, but never the underlying reasons for the rules it seems. This actually makes sense. Thank you. I don't think I will forget it again. I drew it out with three examples!! 