Question

Enumerați elementele mulțimilor
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Answer 1

Salut! :)

x² + x = 2 × ( 1 + 2 + 3 + ... + 2021 )

x × ( x + 1 ) = 2 × ( 2021 × 2022 : 2 )

x × ( x + 1 ) = 2021 × 2022 => x = 2021 => H = { 2021 }