| 1 | 1 | 1 | 1 | |||||
Oblicz sumę | + | + | +...+ | |||||
| 1*3 | 3*5 | 5*7 | 2013*2015 |
| 2 | 1 | 1 | |||
= | − | ||||
| n(n+2) | n | n+2 |
| 1 | ||
To wyciągnij | przed nawias z każdego ułamka  MYŚL | |
| 2 |
| 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | ||||||||||
to wyszło mi | ( | − | )+ | ( | − | )+ | ( | − | )+... | |||||||||
| 2 | 1 | 3 | 2 | 3 | 5 | 2 | 5 | 7 |
| 1 | 1 | 1 | 1 | 1 | 1 | ||||||
( 1 − | + | − | + ... + | − | ) = ... | ||||||
| 2 | 3 | 3 | 5 | 2013 | 2015 |