Solve 1729 as Sum of 2 Cubes: Natural Numbers

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In summary, the conversation is discussing the smallest positive integer, 1729, that can be represented as the sum of two cubes in two different ways. The participants suggest using the formula x^3 + y^3 = 1729 and factoring 1729 to find two factors that fit the formula. They also mention a method using complex numbers and moduli, and reference a well-known story about this question and number.
  • #1
cragar
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Homework Statement


1729 is the smallest positive integer that can be represented in two different ways as the sum of two cubes , what are the two ways.
They have to be natural numbers.

The Attempt at a Solution



x^3+Y^3=1729 i could just find the answer by guess and check , but I am not sure how to do it analytically.
 
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  • #2
You can simplify a little by using [itex]x^3+ y^3= (x+ y)(x^2- xy+ y^2)[/itex].

Now, factor 1729 to find two factors that would fit that.
 
  • #3
sweet thanks for the help
 
  • #4
I remember my teacher showing us a method with complex numbers and moduli to find the sum of two squares to equal some number we have. If only I remember the method... Maybe this can be extended to the sum of two cubes?
 
  • #5
You can't not know the oft-told tale about this question and this number?
 
  • #6
There is a very oft-told tale about this question with this number many people here will know.
 
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FAQ: Solve 1729 as Sum of 2 Cubes: Natural Numbers

How do you solve 1729 as a sum of two cubes using natural numbers?

To solve 1729 as a sum of two cubes using natural numbers, you need to find two numbers whose cubes add up to 1729. These numbers can be positive or negative, as long as they are both natural numbers.

What are the two cubes that add up to 1729?

The two cubes that add up to 1729 are 1^3 and 12^3. This can be written as 1^3 + 12^3 = 1729.

How do you know that 1 and 12 are the correct numbers for solving 1729 as a sum of two cubes?

The numbers 1 and 12 were discovered by mathematician Srinivasa Ramanujan, who famously stated that 1729 is the smallest number expressible as a sum of two cubes in two different ways. This means that there are only two possible combinations of cubes that add up to 1729, and 1 and 12 are one of them.

Can 1729 be expressed as a sum of two cubes in any other way?

No, 1729 can only be expressed as a sum of two cubes in two different ways: 1^3 + 12^3 and 9^3 + 10^3. This has been proven by mathematicians and is known as the "taxicab number" or "Hardy-Ramanujan number".

Why is it important to find sums of cubes for certain numbers?

Finding sums of cubes for certain numbers can be helpful in number theory and cryptography. It can also be used to solve problems in different fields of science, such as physics and chemistry. Additionally, it showcases the beauty and patterns in mathematics and can inspire new discoveries and breakthroughs.

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