Răspuns:
Explicație pas cu pas:
5 + 10 + 15 + ..... + 2020 - 5 × ( 1 + 2 + 3 + ....+ 404 ) = 0
= 5 × ( 1 + 2 + 3 + .....+ 404 ) - 5 × ( 1 + 2 + 3 + ... + 404 ) =
= 0
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Iata si calculele
5 × ( 1 + 2 + 3 + .....+ 404 ) - 5 × ( 1 + 2 + 3 + ... + 404 ) = 0
= 5 × 404 × ( 1 + 404 ) : 2 - 5 × 404 × ( 1 + 404 ) : 2 =
= 5 × 202 × 405 - 5 × 202 × 405 =
= 1010 × 405 × ( 1 - 1 ) =
= 1 010 × 405 × 0 =
= 0
