11

14

20

23

$a_1\ +\ 10d$

$10a_{1\ }+\ d$

$a_1\ +\ 9\ d$

$9a_{1\ }+\ d$

40

45

35

50

$\frac{n}{2}\left(\ a_1\ +\ a_n\right)$

$\frac{n}{2}\left(\ 2a_1\ +\ \left(n-1\right)d\right)$

$\frac{n}{2}\left(\ \frac{1-\ r^n}{1-r}\right)$

$\frac{a_1\left(1-\ r^n\right)}{1\ -\ r}$

512, 375 , 1024 or 683 , 1365 , 125

-683 , 1365 , -2048 or 683 , 1365 , 2048

-2 , 8 ,-32 or 2 , 8 32

-4 , 32 , -256 or 4 , 32 256