Question

19+22+25+...+2020 care e raspunsul?

Answer 1

19+22+25+...+2020 =

= (3·1+16) + (3·2+16) + (3·3+16) + ... +(3·668+16)

= 3·(1+2+3+...+668) + 16+16+16+...+16 {de 668 ori}

= 3·(668·669)/2 + 16·668

= 3·334·669 + 16·668

= 670338 + 10688

= 681026