Question

cum fac 1+4+7+.....+61ca sa fie suma lui gaos?ajutoor

Answer 1

1+4+7+...+61=(1+0*3)+(1+1*3)+(1+2*3)+...+(1+20*3)=21+0*3+1*3+2*3+...+20*3=21+3*(1+2+3+...+20).

1+2+3+...+20 este suma Gauss, deci te descurci de aici.

Answer 2

1+4+7+...+61=(1+0•3)+(1+1•3)+(1+2•3)+...+(1+20•3)=21+0•3+1•3+2•3+...+20•3=21+3(1+2+3+...+20),iar acum facem suma lui Gauss 1+2+3+...+20 = 20•21/2=420/2=210...sper ca te-am ajutat