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# M04-11

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Intern
Joined: 31 Oct 2016
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10 Apr 2018, 10:52
cant j be an imaginary number for the first statement?
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10 Apr 2018, 11:07
s12345 wrote:
cant j be an imaginary number for the first statement?

1. On the GMAT all numbers used are real numbers.

2. If this were not the case, still |j| = j^(-1) has no complex solution.
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08 Jul 2018, 18:29
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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08 Jul 2018, 19:51
I answered correctly. Difficult questions are getting easier.
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29 Jul 2018, 02:12
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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29 Jul 2018, 02:17
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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29 Jul 2018, 04:09
1
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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29 Jul 2018, 05:10
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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29 Jul 2018, 05:18
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

GMAT online Tutor

Re: M04-11 &nbs [#permalink] 29 Jul 2018, 05:18

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# M04-11

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