Question

Find the 13th term of the arithmetic sequence whose common difference is d=7 and whose first term is a1=-3

Answer 1

81

Explanation:

the formula for an arithmetic sequence:

aₙ = a₁ + (n-1)d

where aₙ = the nth term

a₁ = the 1st term = -3

n = the term number = 13

d = the common difference = 7

Plugging in those values into the formula to find a₁₃:

a₁₃ = -3 + (13-1)7

= -3 + (12)7

= -3 + 84

= 81