Question

Aflati sumele: 4+8+12.....+1996= (va rog si sa.mi explicati) plzz

Answer 1

4+8+12+...+1996=?

Dam factor comun pe 4

4 (1+2+3+...+499)

Suma unor numere consecutive se cu suma lui
Gauss: n(n+1)/2
Deci e

4 (499x500/2)=
4x499x250=499000

Answer 2

$\displaystyle 4+8+12+...+1996=4(1+2+3+...+499)=4 \times \frac{499(499+1)}{2} = \\ \\ =4 \times \frac{499 \times 500}{2} =4 \times \frac{249500}{2} =4 \times 124750=499000$