Will it be still distinct?

Algebra Level 1

3 + 3 = 6 3 3 = 0 3 × 3 = 9 3 ÷ 3 = 1 \begin{aligned} 3 + 3 &= 6 \\ 3 - 3 &= 0 \\ 3 \times 3 &= 9 \\ 3 \div 3 &= 1 \end{aligned}

The above shows 4 equations, where the integer 3 together with 4 operations ( + × ÷ ) (+ - \times \div) produces 4 distinct numbers.

If we use some other integer greater than 3, will it still produce 4 distinct numbers?

Yes, always No, not necessarily

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2 solutions

Kb E
Nov 12, 2017

The second and fourth equations will always be 0 and 1 and the second and fourth equations will be greater than 1 for n > 1 n>1 . So the only condition we need is n + n n n 2 n n 2 n 2 n+n \neq n*n \implies 2n \neq n^2 \implies n \neq 2 . So for any n > 3 n> 3 , four distinct integers will be produced on the right-hand​ side.

Doesn’t it fails for n = 1?

Dan Daughtry - 3 years, 6 months ago

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The question asks for integers equal to or greater than 3.

kb e - 3 years, 6 months ago

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Ah, missed that.

Dan Daughtry - 3 years, 6 months ago
Chew-Seong Cheong
Nov 16, 2017

For n N n \in \mathbb N , we note that n n = 0 n-n=0 and n ÷ n = 1 n \div n = 1 for all n n . The two numbers are always distinct for all n n . For n + n = n × n = n n n+n = n \times n = n-n , n = 0 < 3 \implies n=0 < 3 . We note that n + n 2 n ÷ n n+n \ge 2 \ne n \div n and that for n × n = n ÷ n n \times n = n \div n , n = 1 < 3 \implies n = 1 < 3 . And the last case is n + n = n × n n+n=n\times n , n = 2 < 3 \implies n=2<3 .

Yes, always for integer greater than 3, the four equations will produce four distinct numbers.

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