sum of 3 smallest primes, each 2 more than perfect cube

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owningbro2

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can anyone help me out with this?

what is the sum of the three smallest prime numbers each of which is two more than a perfect positive cube?
 
Re: Help

owningbro2 said:
can anyone help me out with this?

what is the sum of the three smallest prime numbers each of which is two more than a perfect positive cube?
Click to expand...

Please share with us your work/thoughts, so that we know where to begin to help you.

To begin thinking:

Are prime numbers - odd or even?

So what kind of cubes you ought to be looking for?
 
Re: Help

owningbro2 said:
i have no idea where to start or what to begin with....
so sry....
Click to expand...

So start by answering the two questions - I posed in front of you. I'll walk you through the problem step by step.
 
Re: Help

so im guessing you know how to do the problem....

the prime numbers are odds and im looking for perfect positive cubes.
 
Re: Help

I would start by making a list of perfect cubes. Then I would add 2 to each of those and see if I can see something that satisfies the sought after condition.
 
Re: Help

owningbro2 said:
so im guessing you know how to do the problem....

the prime numbers are odds and im looking for perfect positive cubes.
Click to expand...

So now..

each of these odd numbers are 2 more than cube of numbers.

so the number to get cube of must be odd - because cube of odd numbers will be odd numbers and adding 2 to those will still be odd.

So let us lest the odd numbers - and their cubes - and 2 more than each of those.

like below

number..........cube............cube+2

1..................1.................3

3..................27...............29

5.................125..............127

...

and so on....

Now on the column to the right (cube+2) - choose the prime numbers.

show us what you find.
 
Re: Help

owningbro2 said:
what is a perfect cube?
Click to expand...

I think - in this context - perfect cube simply refers to cube of integers.
 
Re: Help

owningbro2 said:
this is why i need help....
Click to expand...

Loren gave you an excellent suggestion. Make a list of the cubes of the positive integers (Oh gee...I just saw that you do not know what a perfect cube is!!):

1^3 = 1*1*1 = 1.....so 1 is a perfect cube
2^3 = 2*2*2 = 8.....so 8 is a perfect cube
3^3 = 3*3*3 = 27.....so 27 is a perfect cube
etc.

Then....try adding 2 to each of those cubes. Do you get a prime number? Take the three SMALLEST prime numbers you get this way.

Now...your problem does not specify that the three primes must be different...it makes a huge difference if they must be.

If they are NOT required to be different, note that 1^3 = 1. Add 2 to this, and you get 3, which is a prime number. Now, if you can use 3 for each of the numbers, then 3 + 3 + 3, or 9 is the smallest possible sum you can get. Since this is a very simplistic answer, I suspect that it is not "all there is" to the problem.
 
Re: Help

cant find any perfect cube is i add 2 to it will come out to a prime number for example i went to 22 cubed and got nothing.... so i need to know which perfect cube plus 2 is a prime number and i need three of them.
also, need to know if 1 is perfect cube then if it is then it would be a perfect cube and adding 2 to it would turn it into a prime number (3) this is because some people say it is and some say it is not.

the perfect cubes of which i got that when you add 2 to it would turn into is/are....

3 cubes equals 27 +2 would be 29 a prime number...
5 cubed equal 125 +2 would be 127 a prime number....
need the third one or to see if 1 a perfect cube....
 
Re: Help

i got it....

perfect cube...perfect cube multiplied...plus added 2...equals prime...
1 cubed = 1 +2 = 3
3 cubed = 27 +2 = 29
5 cubed = 125 +2 = 127
------
this equals 159.....

Thank You,
Subhotosh Khan,
Loren,
Mrspi,
and my brother....
thank you all ! please confirm that the answer is right....
 
Re: Help

i got it....

perfect cube...perfect cube multiplied...plus added 2...equals prime...
1 cubed = 1 +2 = 3
3 cubed = 27 +2 = 29
5 cubed = 125 +2 = 127
------
this equals 159.....
Click to expand...

0[sup:1etcku3c]3[/sup:1etcku3c] = 0
add 2 ...
0[sup:1etcku3c]3[/sup:1etcku3c] + 2 = 2 , and 2 is the only even prime number.
 
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