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nruthya.rajagopal
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guide 1 algebra inequalities and absolute value strategy

by nruthya.rajagopal Tue Nov 06, 2012 8:20 pm

Hi Tommy,
the question is -4<a<4 and -2<b<-1, which of the following could NOT be the value of ab?

options are
a.-3
b.0
c.4
d.6
e.9

lower limit :gt(-4) * gt(-2) = gt (8)
upper limt :lt(4) * lt(-1)= lt (-4)
answers-b,c,d,a;
answer is E .The explaination given confuses me .why should we multiply gt(-2)*gt(4)
and gt(-4) and gt(-2)

Please clarify it.

thanks
Nruthya
nruthya.rajagopal
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Re: guide 1 algebra inequalities and absolute value strategy

by nruthya.rajagopal Fri Nov 09, 2012 1:02 am

please reply soon.

Thanks
Nruthya
tommywallach
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Re: guide 1 algebra inequalities and absolute value strategy

by tommywallach Sat Nov 10, 2012 9:04 pm

Hey nruthya,

You're multiplying in order to define the ENTIRE range of possible values for ab. Once you have that, any answer choice that fits within the range is viable.

So the biggest ab can be is -4 * -2 = 8 (but it has to be LESS than that because of the original inequalities), and the smallest it can be is -1 * 4 = -4 (but it has to be GREATER than that, because of the original inequalities).

So anything within the range -4 to 8 is a possible value of ab.

If that doesn't make sense, you could just test them all:

a.-3 --> -1 * 3
b.0 --> 0 * anything
c.4 --> -1.333333 * -3
d.6 --> -3.5 * -(6/3.5) [You could calculate this with a calculator, or just look at it and know it's slightly greater than -2, so within the viable range of B]

It's much easier to just find the range, though.

-t
nruthya.rajagopal
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Re: guide 1 algebra inequalities and absolute value strategy

by nruthya.rajagopal Tue Nov 13, 2012 3:33 am

Thanks tommy, that make sense.sorry i didn't see that NOT in the question . 9 is out of range.
tommywallach
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Re: guide 1 algebra inequalities and absolute value strategy

by tommywallach Thu Nov 15, 2012 5:42 pm

Ha! Indeed, missing the NOT does make it confusing! : )

-t
manigraja100
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Re: guide 1 algebra inequalities and absolute value strategy

by manigraja100 Sun Jun 23, 2013 12:43 pm

Hi Tommy,
Thanks for ur explanation. pls note that the smallest "ab" can be is not -1 * 4 = -4 but -2 * 4 = -8.
hope i'm correct.
tommywallach
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Re: guide 1 algebra inequalities and absolute value strategy

by tommywallach Wed Jun 26, 2013 7:04 pm

You're right, Mani! Good catch!

-t