u_n=u_n-1+d

d is the common difference

u_n=u₁+(n-1)d

d is the common difference

Arithmetic Partial Sum

(u₁ and u_k are given)

_k                           

∑   u_n=k/2(u₁+u_k)

ⁿ⁼¹                           

Arithmetic Partial Sum

(u₁ and d are given)

_k                                    

∑   u_n=ku₁+[k(k-1)/2]d

ⁿ⁼¹                                 

d is common difference

u_n=ru_n-1

r is the common ratio

u_n=u₁r^n-1

r is the common ratio

_k                                 

∑   u_n=u₁[(1-r^k)/(1-r)]

ⁿ⁼¹                                  

r is the common ratio