Question

2+4+6+8+.....+288= va rog!!!

Answer 1

Dăm factor comun:
2x1+2x2+2x3+2x4+...+2x144=
=2x(1+2+3+4+...+144)=
Formula sumei lui Gauss: 1+2+...+n=n x (n+1):2
=2x 144(144+1):2=
=2x 144x145:2=
= 288 x 145:2=
= 41760:2=
=20 880.

Answer 2

2+4+6+8+.....+288=
=2(1+2+..+144)
=2·144·145:2
=144·145
=20880