Differences

Differences

Posers and Puzzles

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r

Joined
08 Dec 03
Moves
3140
03 Jun 04

Can you find the two smallest whole numbers where the difference of their squares is a cube, and the difference of their cubes is a square?

-Ray.

Zeist, Holland

Joined
11 Sep 03
Moves
19384
03 Jun 04
1 edit

Guess you forgot the word 'different'?

0^2-0^2=0^3
0^3-0^3=0^2

In case this is true, you could take 6 and 10:

10^2-6^2 = 100-36 = 64 = 8^3
10^3-6^3 = 1000-216 = 784 = 28^2

Are these the smallest?

r
CHAOS GHOST!!!

Elsewhere

Joined
29 Nov 02
Moves
17317
03 Jun 04

1^3 - 0^3 = 1^2

1^2 - 0^2 = 1^3

Zeist, Holland

Joined
11 Sep 03
Moves
19384
03 Jun 04

Originally posted by royalchicken
1^3 - 0^3 = 1^2

1^2 - 0^2 = 1^3
Yes; but that is quite trivial. Maybe we should add the requirement that there is no zero involved?

r

Joined
08 Dec 03
Moves
3140
04 Jun 04

The problem did request whole numbers. There seems to be ambiguous definitions for the set of whole numbers. In this case, the set of whole numbers was intended to be the set of positive integers.

In this case, the correct numbers are indeed 6 and 10.

-Ray.

Zeist, Holland

Joined
11 Sep 03
Moves
19384
04 Jun 04

The set of whole numbers is: -inf,...,-3,-2,-1,0,1,2,3,...,inf
Then there are the natural numbers: 0,1,2,3,...,inf
You wanted the natural numbers^+: 1,2,3,...,inf

Might be handy to remember; it stops lots of confusion 😀

Now With Added BA

Loughborough

Joined
04 Jul 02
Moves
3790
04 Jun 04

Originally posted by piderman
The set of whole numbers is: -inf,...,-3,-2,-1,0,1,2,3,...,inf
Then there are the natural numbers: 0,1,2,3,...,inf
You wanted the natural numbers^+: 1,2,3,...,inf

Might be handy to remember; it stops lots of confusion 😀
I take the natural numbers or N to exclude zero - after all zero was not thought to be a number at all in the past, so it's hardly 'natural' from a human perspective, and it's not really a counting number either, unless you're a computer scientist. If I need to write 'the natural numbers with zero' I write Z subscript(at least 0) (looks better with the appropriate symbols). I suppose I could use Z subscript(strictly greater than 0) instead of N, as that would also be unambiguous.

T
Kupikupopo!

Out of my mind

Joined
25 Oct 02
Moves
20443
06 Jun 04

Lol, piderman. You give the most trivial solution of all, assume the author meant different numbers, then make a point of someone giving the most trivial solution to your extra condition, you should be more precise in your conditions :p