Question

3+8+12+18+23+ ... +83
Rapid, vă rog, dau coroană.

Answer 1

$S=3+8+12+...+83$

$S=83+78+73+...+3$

$2S=86+86+86+...+86$

$Nr \ termeni=\frac{83-3}{8-3}+1=\frac{80}{5}+1=17$

$2S=17*86$

$S=17*43$

$S=731$