Question

Cum se calculeaza 6 + 12 + ... + 288? Dar 1 + 3 + 5 + ... + 101? (As dori o explicatie decat rezultatul, multumesc.)

Answer 1

6+12+...+288=
=6×1+6×2+...+6×48=
=6×(1+2+3+...+48)=
=48×49:2=24×49=1176

1+3+5+...+101=1+2+3+4+5+6+...+100+101-2×(1+2+3+...+50)=
=101×102:2-2×50×51:2=
=101×51-100×51=51×(101-100)=51×1=51