Question

3+6+9+....+45 cum se calculeaza va rog

Answer 1

3+6+9+...+45=

3(1+2+3+...+15)=

=3x15x16:2=3x15x8=24x15=360

,,x”=înmulțit

Answer 2

3+6+9+....+45 = 3×(1+2+3+....+15)

Suma liu Gauss  1+2+3+....+n = [n(n+1)]/2

1+2+3+....+15 = [15(15+1)]/2 = 240/2 = 120

3×(1+2+3+....+15) = 3×120 = 360