Math Is Fun Forum

Are you trying to say :
{
x² - y² = (x+y)(x-y)
where x, y are positive integers
and (x-y) is positive
x² - y² is therefore a composit number (non prime) with factors (x-y) and (x+y)
}
?

But are you sure every non-prime can be generated with this? How about one that is compost of an odd factor and an even factor?

For example:
70 = 10 * 7 = (x+y)(x-y)
x = ½ ( 10+7 ) = 8.5
y = ½ ( 10-7 ) = 1.5

I think you have to work with decimals in order for this to produce 'any non-prime' ...

200³ =  2 000² + 2 000² = 8 000 000

196³ =  2 744² = 7 529 536

2580^2+450^2+10^2 = 6859000 = 190^3

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