Расчет: oQttXp - 1
S_n =
| ( 2* a_1+ d* (n-1))* n |
| / 2 |
|
S_n =
$$S_{n}$$ = $$\frac{(2\cdot a_{1}+d\cdot (n-1))\cdot n}{2}$$
| ( 2* a_1+ d* (n-1))* n |
| / 2 |
S_n = a_1* n+
-
$$S_{n}$$ = $$a_{1}\cdot n+\frac{n^{2}\cdot d}{2}-\frac{d\cdot n}{2}$$
| n^2* d |
| / 2 |
| d* n |
| / 2 |
S_n = a_1* n+ 0.5* d* n^2- 0.5* d* n$$S_{n}$$ = $$a_{1}\cdot n+0.5\cdot d\cdot n^{2}-0.5\cdot d\cdot n$$