Question

Calculați 4+7+10+...+2704​

Answer 1

S = 4+7+10+...+2704

S = (3•1+1)+(3•2+1)+(3•3+1)+...+(3•x+1)

2704:3 = 901 rest 1

⇒ 2704 = 3•901 + 1 ⇒ x = 901

S = (3•1+1)+(3•2+1)+(3•3+1)+...+(3•901+1)

S = 3•(1+2+3+...+901) + 1+1+...+1

{1 de 901 ori}

S = 3•901•902/2 + 1•901

S = 3•901•451 + 901

S = 901•(1353 + 1)

S = 901•1354

⇒ S = 1219954