Question

Find the sum of the arithmetic sequence 1, 4, 7, 10, ...,94; n=32

Answer 1

Explanation:

hello :

the sum is : Sn = n/2(U1 + Un ) and U n = U1+(n-1)r

given : U1 = 1 r=4-1=7-4=...= 3 n= 32

so : U 32 = 1+(32-1)3= 94

S32 = 32/2 (1+94) = 1520