:Help...........for how many positive integers n is n^3 -8n^2+20n-13 a prime number??

- King

:Help...........for how many positive integers n is n^3 -8n^2+20n-13 a prime number??

- Stacey Warren - Expert brainly.com

Hey! We 've verified this expert answer for you, click below to unlock the details :)

At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.

- katieb

I got my questions answered at brainly.com in under 10 minutes. Go to brainly.com now for free help!

- anonymous

factorize it

- King

how watever i get is not a prime number

- King

why?

Looking for something else?

Not the answer you are looking for? Search for more explanations.

## More answers

- King

oh

- King

but then ii have to plug in millions of values

- anonymous

what u want to calculate

- anonymous

(n^3 -8n^2+20n-13) a prime number

- anonymous

or n is a prime number

- King

for n i will have to put millions of values to find how may n positive integers satisfy n^3 -8n^2+20n-13 to be a prime number

- anonymous

ok

- King

so,what to do??

- King

anything i can do to narrow down the possobilities

- King

no answer given....

- anonymous

ok see for 2 it is prime number

- anonymous

wait i took wrong concept

- anonymous

\[(x-1) \times [(x-7)x + 13]\]

- anonymous

where x is n

- King

ok

- anonymous

now see the first term is (x-1). and other than 2 no other even number is a prime number right

- anonymous

i got the answer

- King

no n does not have to be a prime number n^3 -8n^2+20n-13 has to be a prime number

- anonymous

yeah i know (x−1)×[(x−7)x+13] it has to be prime

- King

yup so x can be anything greater or equal to 2

- anonymous

first term is (x-1) and two is the only even prime number.

- anonymous

but if u will subtract 1 from any other prime number the resultant will be divisible by 2

- anonymous

getting my point or not

- King

x can be 4

- anonymous

yeah u r right

- anonymous

it means that for any odd integer other than 3 u will not get a prime number

- King

yeah

- anonymous

Superb sheggy!

- anonymous

also the number cannot be graeter than 7

- King

oh yeah

- anonymous

thanks fool bhai

- anonymous

so u are having a limited space to work out that is from 1 to 7

- King

yes sheg u got it so answer is n=2,3,4

- King

no actually 2 to 7

- anonymous

hahahaa right 2 to 7

- anonymous

but for 7 it will be 0

- King

wait why cant it be greater than 7?

- anonymous

try any number u will get the answer

- anonymous

odd numbers cannot be included ok thats true

- anonymous

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

- King

is 323 a prime number?

- King

yeah i acept

- King

its not div by 17

- anonymous

323 is divisible by 17

- anonymous

so 323 is not a prime number

- King

4387 ?

- anonymous

what u have put x = ??

- King

n=20

- King

1443?

- King

gtg shall come bak in 15 min

- anonymous

for n = 20 it should be equal to 5187

- King

oh yeah 1443?

- King

no

- anonymous

20^3 - 8*20^2 + 20*20 -13 =8000 - 3200 + 400 -13 = 8400 - 3213 = 5187

- King

gtg cum bak in 15 mins

- anonymous

dear i had told u for no value greater than 7 it would fit

- anonymous

and both 1443 and 5187 is divisible by 3

- King

i am bak so what to do now?

- anonymous

for no value greater than 7 that too even number it will not be a prime number

- anonymous

http://www.wolframalpha.com/input/?i=x^3-8x^2%2B20x-13+where+x+%3D+20 visit this website and plug in different value of x u will get the answer

- anonymous

king u there

Looking for something else?

Not the answer you are looking for? Search for more explanations.