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M04-11

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Re: M04-11  [#permalink]

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New post 10 Apr 2018, 09:52
cant j be an imaginary number for the first statement?
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New post 10 Apr 2018, 10:07
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New post 08 Jul 2018, 17:29
Hi Bunnel
In option 1 for rewriting , we have multiplied by j on the both sides. This we can do if we are clear about sign of j , means j>0,
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New post 08 Jul 2018, 18:51
I answered correctly. :cool: Difficult questions are getting easier. :shocked
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New post 29 Jul 2018, 01:12
Bunuel niks18 gmatbusters KarishmaB amanvermagmat chetan2u


Quote:
If \(j \ne 0\), what is the value of \(j\) ?


(1) \(|j| = j^{-1}\)

(2) \(j^j = 1\)


Is it correct to write: |j| * j = 1 as \(j^2\) = 1
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New post 29 Jul 2018, 01:17
adkikani wrote:
Bunuel niks18 gmatbusters KarishmaB amanvermagmat chetan2u


Quote:
If \(j \ne 0\), what is the value of \(j\) ?


(1) \(|j| = j^{-1}\)

(2) \(j^j = 1\)


Is it correct to write: |j| * j = 1 as \(j^2\) = 1


Only when j is positive. When j is negative we'll get -j^2 = 1, which does not have real roots.
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New post 29 Jul 2018, 03:09
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adkikani wrote:
Bunuel niks18 gmatbusters KarishmaB amanvermagmat chetan2u


Quote:
If \(j \ne 0\), what is the value of \(j\) ?


(1) \(|j| = j^{-1}\)

(2) \(j^j = 1\)


Is it correct to write: |j| * j = 1 as \(j^2\) = 1


No, you cannot because you do not know what is j, is it positive or negative?
If \(j^2=1\), only thing that you can say is |j|=1 that is j=1 or j=-1
If j=1 |j|*j=|1|*1=1 but if j=-1, |j|*j=|-1|*-1=1*-1=-1
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


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Re: M04-11  [#permalink]

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New post 29 Jul 2018, 04:10
Thanks chetan2u for your prompt response.

You wrote:
Quote:
No, you cannot because you do not know what is j, is it positive or negative?


Quote:
but if j=-1, |j|*j=|-1|*-1=1*-1=-1


But RHS of equation : |j| * j = 1 is Positive 1 and this excludes
possibility of -1 in your steps. Am I and Bunuel not on same page with
slight change in perception?
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Re: M04-11  [#permalink]

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New post 29 Jul 2018, 04:18
adkikani wrote:
Thanks chetan2u for your prompt response.

You wrote:
Quote:
No, you cannot because you do not know what is j, is it positive or negative?


Quote:
but if j=-1, |j|*j=|-1|*-1=1*-1=-1


But RHS of equation : |j| * j = 1 is Positive 1 and this excludes
possibility of -1 in your steps. Am I and Bunuel not on same page with
slight change in perception?


I started the steps with
'if j^2=1"
You cannot write |j|*j=1 because j can be positive or negative.

Then I gave two cases
if j =1, yes |j|*j=1...(I)
But if j=-1, |j|*j =1 is not correct...(II)

Say we were given |j|*j=1, then case (I) that is j=1
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


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Re: M04-11 &nbs [#permalink] 29 Jul 2018, 04:18

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