Question

What is the sum of the arithmetic sequence 8, 14, 20..., if there are 22 terms?

Answer 1

a1 = 8
a22 = 8 + 6*21
a22 = 8 + 126
a22 = 134
formula : (n+1 ) * (a0 + an) /2
a0 = 8
an = 134
you can do the rest iguess :)

Answer 2

I would solve like this: find a formula for the sequence. an=n*6+2 seems to do. Then, sum from i = 1 to 22: (i*6 + 2). Manipulate that sum a bit. Use some properties of summation to break it down. You should reach 44+6 * (1+2+3+....+22). There's a formula for the last bit.

Answer 3

my options are 1,558
1,560
1,562
1,564

Answer 4

better get calculating then.

Answer 5

for arithmetic sequences, an = a1+ (n-1)d and Sn= (a1+an)(n)/2

d=6, a22=8+21(6)=134
S22=(8+134)(22)/2= 142(11)= 1562

Answer 6

so it was 1562