Question

Va rog repede:8+16+24+...+2504

Answer 1

exista o formula pentru 1+2+3+...+n= n (n+1) totul supra2

8+16+24+...+2504= 8 ( 1+2+3+...+313) = 8x 313x314 totul supra 2= (simplificam 314 cu 2)= 8x313x157=393128

Answer 2

$\displaystyle 8+16+24+...+2504=8(1+2+3+...+313)= \\ \\ =8 \times \frac{313(313+1)}{2} =8 \times \frac{313 \times 314}{2} =8 \times \frac{98282}{2} = \\ \\ =8 \times 49141=393128$