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:Help...........for how many positive integers n is n^3 8n^2+20n13 a prime number??
 2 years ago
 2 years ago
:Help...........for how many positive integers n is n^3 8n^2+20n13 a prime number??
 2 years ago
 2 years ago

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KingBest ResponseYou've already chosen the best response.0
how watever i get is not a prime number
 2 years ago

KingBest ResponseYou've already chosen the best response.0
but then ii have to plug in millions of values
 2 years ago

shegBest ResponseYou've already chosen the best response.1
(n^3 8n^2+20n13) a prime number
 2 years ago

KingBest ResponseYou've already chosen the best response.0
for n i will have to put millions of values to find how may n positive integers satisfy n^3 8n^2+20n13 to be a prime number
 2 years ago

KingBest ResponseYou've already chosen the best response.0
anything i can do to narrow down the possobilities
 2 years ago

shegBest ResponseYou've already chosen the best response.1
ok see for 2 it is prime number
 2 years ago

shegBest ResponseYou've already chosen the best response.1
\[(x1) \times [(x7)x + 13]\]
 2 years ago

shegBest ResponseYou've already chosen the best response.1
now see the first term is (x1). and other than 2 no other even number is a prime number right
 2 years ago

KingBest ResponseYou've already chosen the best response.0
no n does not have to be a prime number n^3 8n^2+20n13 has to be a prime number
 2 years ago

shegBest ResponseYou've already chosen the best response.1
yeah i know (x−1)×[(x−7)x+13] it has to be prime
 2 years ago

KingBest ResponseYou've already chosen the best response.0
yup so x can be anything greater or equal to 2
 2 years ago

shegBest ResponseYou've already chosen the best response.1
first term is (x1) and two is the only even prime number.
 2 years ago

shegBest ResponseYou've already chosen the best response.1
but if u will subtract 1 from any other prime number the resultant will be divisible by 2
 2 years ago

shegBest ResponseYou've already chosen the best response.1
it means that for any odd integer other than 3 u will not get a prime number
 2 years ago

shegBest ResponseYou've already chosen the best response.1
also the number cannot be graeter than 7
 2 years ago

shegBest ResponseYou've already chosen the best response.1
so u are having a limited space to work out that is from 1 to 7
 2 years ago

KingBest ResponseYou've already chosen the best response.0
yes sheg u got it so answer is n=2,3,4
 2 years ago

KingBest ResponseYou've already chosen the best response.0
wait why cant it be greater than 7?
 2 years ago

shegBest ResponseYou've already chosen the best response.1
try any number u will get the answer
 2 years ago

shegBest ResponseYou've already chosen the best response.1
odd numbers cannot be included ok thats true
 2 years ago

shegBest ResponseYou've already chosen the best response.1
as i had told u any odd number subtracted by one will result in even number so it will be divisible by 2.........do u accept it or not
 2 years ago

shegBest ResponseYou've already chosen the best response.1
so 323 is not a prime number
 2 years ago

KingBest ResponseYou've already chosen the best response.0
gtg shall come bak in 15 min
 2 years ago

shegBest ResponseYou've already chosen the best response.1
for n = 20 it should be equal to 5187
 2 years ago

shegBest ResponseYou've already chosen the best response.1
20^3  8*20^2 + 20*20 13 =8000  3200 + 400 13 = 8400  3213 = 5187
 2 years ago

shegBest ResponseYou've already chosen the best response.1
dear i had told u for no value greater than 7 it would fit
 2 years ago

shegBest ResponseYou've already chosen the best response.1
and both 1443 and 5187 is divisible by 3
 2 years ago

KingBest ResponseYou've already chosen the best response.0
i am bak so what to do now?
 2 years ago

shegBest ResponseYou've already chosen the best response.1
for no value greater than 7 that too even number it will not be a prime number
 2 years ago

shegBest ResponseYou've already chosen the best response.1
http://www.wolframalpha.com/input/?i=x^38x^2%2B20x13+where+x+%3D+20 visit this website and plug in different value of x u will get the answer
 2 years ago
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