Question

Identify the 42nd term of an arithmetic sequence where a1 = -12 and a27 = 66.

70
72
111
114

Answer 1

first,
a27 = 66 means
a1 + (27-1)d = 66
-12 + 26d = 66
solve for d

Answer 2

3

Answer 3

yep.. correct

Answer 4

k

Answer 5

now, to get a42 use the formula :
an = a1 + (n-1)d
a42 = -12 + (42-1)3
a42 = -12 + 41(3) = ... ?

Answer 6

got it ?

Answer 7

what's 41 times 3 .....
then subtracted by 12

Answer 8

111, !

Answer 9

cool :D