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NL
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Re: Tricky DS Please help

by NL Thu Apr 10, 2014 11:11 pm

Sorry, I still failed to take a shovel and dig. Will do.
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Re: Tricky DS Please help

by jnelson0612 Sat Apr 12, 2014 6:10 pm

NL Wrote:Sorry, I still failed to take a shovel and dig. Will do.


:-)
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Re: Tricky DS Please help

by NL Sun Apr 20, 2014 9:53 pm

RonPurewal Wrote:* If you just shuttle the absolute-value bars to the other side of each of these equations, the resulting equations, x + 3 = |4x - 3| and x + 1 = |2x - 1|, have two solutions each.


That’s because only negative numbers need to get into | | to be equal with the other side, (of course I didn’t know it until you pointed out.)

Yeah, sometimes I jumped to conclusions without considering a lot of other cases. But I see your point here. Nice!
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Re: Tricky DS Please help

by RonPurewal Mon Apr 21, 2014 5:33 pm

NL Wrote:Yeah, sometimes I jumped to conclusions without considering a lot of other cases. But I see your point here. Nice!


In general, you can avert a lot of mental acrobatics by just working out the problem.
Unless something is genuinely going to take 5+ minutes to do (an extreme rarity on this test), it's best just to do the work, unless you know exactly how everything is going to turn out.
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Re: Tricky DS Please help

by NL Wed Apr 30, 2014 3:56 pm

NL Wrote:Re-written questions:

E.g. 1: Bad a-Good a
(Changing statement 1)
Is a >0?
(1) |3a| = a-8
(2) (a-1)^9 > -1


Hehe, the re-written statement (1) is still...bad. Sorry Ron. But why didn't you tell me? I didn’t test the numbers carefully. It should be written like this:

(1)|a| = 3a-8
or something like these also work:
|1/3a| = 1/2a -1
|2a| = 3a-8
|10a| = 100a-1/100
etc.

Something looking like these don’t work:
|1/2a| = 1/3a-1
|1/2a|= -1/3a-1
|3a| =2a-8
|100a|= 10a- 1/100
etc.

Do you know why?

P/s: I edited the question 1 again in the previous post and provided answers. Please let me know any other problems in them. Thanks.
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Re: Tricky DS Please help

by RonPurewal Thu May 01, 2014 7:39 am

Since this discussion has evolved into something completely unrelated to the problem in the thread, I'd suggest that you move it to the general math folder if you want to continue having it.

Thanks.
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Re: Tricky DS Please help

by NL Sat May 03, 2014 5:21 pm

This is called "brute force", but I have no choice. So "just do the work"!
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Re: Tricky DS Please help

by RonPurewal Sun May 04, 2014 11:16 am

Something like that.