OG math.
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- givemeanid
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'could be' is the key. Question is not asking which value will 'always be' a prime. Check other choices and you will realize there is no value of X for which the other choices will ever be true.
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If X is a prime number greater than 2.Which of the following could be a prime number??aditya33 wrote:If X is a prime number greater than 2.Which of the following could be a prime number??
1-X^2
2-X/2
3-3X
4-X-4
5-X^2+1..
Ans is:- d (X-4)..But if i choose 13 as a prime number then it could be 13-4=9 which is not a prime numeber.Although 11-4=7 which is a prime no.So,this ans gives us two different answers..I am confused which one should be correct..
Plss help.
It means is there any choice that can be a prime no. for X.
Only option D full fill this possibility.
Regards,
Farooq Farooqui.
London. UK
It is your Attitude, not your Aptitude, that determines your Altitude.
Farooq Farooqui.
London. UK
It is your Attitude, not your Aptitude, that determines your Altitude.
Although the other posters seem to have answered your question, I thought I could provide slightly more detail.aditya33 wrote:If X is a prime number greater than 2.Which of the following could be a prime number??
1-X^2
2-X/2
3-3X
4-X-4
5-X^2+1..
Ans is:- d (X-4)..But if i choose 13 as a prime number then it could be 13-4=9 which is not a prime numeber.Although 11-4=7 which is a prime no.So,this ans gives us two different answers..I am confused which one should be correct..
Plss help.
1- x^2 can't be a prime because it will be divisible by 1, x^2, and x.
2- x/2 can't be prime because x is odd and an odd divided by 2 is not an integer
3- 3x can't be prime because it will have 1, x, and 3 as factors.
4- you proved this one yourself
5- x^2+1 can't be prime because if x is odd (as question says it is) than once you add 1 it will be an even. No even greater than 2 is a prime.
Hope that was helpful.