Question

Ma puteți ajuta la acest exrcitiu? Va rog frumos!

Answer 1

Explicație pas cu pas:

S=2+6+10+...+114

S=2(1+3+5+...+57)

S=2*57(57+1)/2

S=58*57

S=3306

Bafta!

Answer 2

A=2+6+10+...+110+114=

=2×1+2×3+2×5+....+2×55+2×57=

=2×(1+3+5+7+...+55+57)=

=2×[(1+2+3+5+6+7+....+55+56+57)-(2+4+6+...+56)]=

=2×[(57×58:2)-2×(1+2+3+...+28)]=

=2×[(57×29)-2×(28×29:2)]=

= 2×[1653-2×(14×29)]=

=2×(1653-2×406)=

=2×(1653-812)=

=2×841=

=1682