1−xn | ||
∑k=0n−1xk= | ||
1−x |
(n−1)xn−nxn−1−1 | ||
∑k=0n−1kxk−1= | ||
(x−1)2 |
nxn+1−(n+1)xn−1 | ||
∑k=1nkxk−1= | ||
(x−1)2 |
1−an | 1−an−1 | 1−a2 | ||||
Sn= | +a | +...+an−2 | +an−1= | |||
1−a | 1−a | 1−a |
1−an+a−an+a2−an+...+an−2−an+an−1 | ||
= | = | |
1−a |
1+a+a2+...+an−1−(n−2)an |
| |||||||||
= | = | = | ||||||||
1−a | 1−a |
1−an−(n−2)(1−a)an | ||
= | ||
(1−a)2 |
5^2 | 52 |
2^{10} | 210 |
a_2 | a2 |
a_{25} | a25 |
p{2} | √2 |
p{81} | √81 |
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