Prove that two sequences of integers that have the same sum and product must be the same.

163 Views Asked by At

Given two sequences of nondecreasing distinct positive integers such that $$x_1 + x_2 + ... + x_i = y_1 + y_2 + ... + y_i , i>0$$ and that $$x_1x_2 ... x_i = y_1y_2 ... y_i$$ Prove/disprove that the sequences are equal i.e. $$x_1 = y_1, x_2 = y_2, ... , x_i = y_i$$

I started with
Let $x_1x_2 ... x_i$ be $A$. If $A$ is prime, $x_1 = A = y_1$ (since $A$ cannot be factored any more) and we are done.

What I don't know is what happens when $A$ is not prime. Intuitively, it sounds true, and I cannot find any counter examples.

2

There are 2 best solutions below

4
On BEST ANSWER

Counterexample:

$12+4+3 \ =\ 9+8+2$

$12\cdot4\cdot3 \ = \ 9\cdot8\cdot2$

Moreover, for $\ i>2\ ,\ $you can always find infinitely many counterexamples.

2
On

Let $x_1 = y_2, x_2 = y_1$ for a quick counter example.