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Retired Moderator
Joined: 19 Nov 2020
Posts: 326
Given Kudos: 64
GRE 1: Q160 V152
What is the remainder ...
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Updated on: 02 Aug 2021, 09:59
Updated on: 02 Aug 2021, 09:59
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Question Stats:
83% (02:10) correct
16% (02:59) wrong based on 6 sessions
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What is the remainder of \((x^3-x)(x^7-x)/21\), if x is a whole number ?
(A) 4
(B) 3
(C) 2
(D) 1
(E) 0
(A) 4
(B) 3
(C) 2
(D) 1
(E) 0
Originally posted by motion2020 on 30 Jul 2021, 13:15.
Last edited by motion2020 on 02 Aug 2021, 09:59, edited 1 time in total.
Last edited by motion2020 on 02 Aug 2021, 09:59, edited 1 time in total.
Retired Moderator
Joined: 16 Apr 2020
Status:Founder & Quant Trainer
Affiliations: Prepster Education
Posts: 1546
Given Kudos: 172
Location: India
WE:Education (Education)
Re: What is the remainder ...
[#permalink]
30 Jul 2021, 19:16
30 Jul 2021, 19:16
2
motion2020 wrote:
What is the remainder of \((x^3-x)(x^7-x)/21\) ?
(A) 4
(B) 3
(C) 2
(D) 1
(E) 0
(A) 4
(B) 3
(C) 2
(D) 1
(E) 0
Easiest way is to use numbers
\(x= 2\)
\((2^3-2)(2^7-2) = (6)(126) = (2)(3)(7)(18)\)
Remainder = 0
\(x= 3\)
\((3^3-3)(3^7-3) = (24)(2184) = (8)(3)(7)(312)\)
Remainder = 0
Hence, option E
Retired Moderator
Joined: 19 Nov 2020
Posts: 326
Given Kudos: 64
GRE 1: Q160 V152
Re: What is the remainder ...
[#permalink]
02 Aug 2021, 10:00
02 Aug 2021, 10:00
I have posted this question initially without defining x as a whole number. The question was missing something..
Now, it's fixed.
Now, it's fixed.
motion2020 wrote:
What is the remainder of \((x^3-x)(x^7-x)/21\), if x is a whole number ?
(A) 4
(B) 3
(C) 2
(D) 1
(E) 0
(A) 4
(B) 3
(C) 2
(D) 1
(E) 0
