Question

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

(A) 70
(B) 72
(C) 111
(D) 114

Answer 1

\[a _{n} = a _{1} + (n - 1)d\]

Answer 2

so
\[a _{27} = a _{1} + (27 - 1)d\]

Answer 3

Which part do I do first?

Answer 4

see u r having the values of a27 and a1....just plug those and get the common difference "d"

Answer 5

and after tht find a42

Answer 6

Okay, I am trying it now

Answer 7

Would it look like this?
\[66=-12+(27-1)\]

Answer 8

hmmm...wht about "d" ????

Answer 9

@sunmidge done??

Answer 10

Is "d" 42?

Answer 11

\[66=-12+(27-1)42\]

Answer 12

Is this correct??? sorry, I am terrible at math

Answer 13

nah....u need to find "d" i.e common difference.....plug values in the equation
\[a _{27} = a_{1} + (n - 1)*d\]

Answer 14

and u r given
[a _{27} = 66\]
\[a _{1} = -12\]
n = 27
get "d"