Question

Identify the 42nd term of an arithmetic sequence where a_1 = −12 and a_27 = 66.

Answer 1

A. 70
B. 72
C. 111
D. 114

Answer 2

do you know the n'th general term formula for arithmetic sequence ?

Answer 3

No but I think the answer is C. 111

Answer 4

did you calculate it ?

Answer 5

The best I know how... I'm not sure if I have done it right though
a(n) = a(1) + (n - 1)d
a(1) = -12
a(n) = -12 + (n - 1)d
a(27) = 66
66 = -12 + (27 - 1)d
66 = -12 + 26d
26d = 66 + 12
26d = 78
d = 78/26
d = 3
a(n) = -12 + 3(n - 1)
a(42) = -12 + 3(42 - 1) = -12 + 3(41) = -12 + 123 = 111

Answer 6

oh wow11 thats correct :)

Answer 7

Awesome! thank you :)

Answer 8

welcome ^_^