Question

Marks: 2
Identify the 42nd term of an arithmetic sequence where a1 = -12 and a27 = 66.
Choose one answer.
a. 70
b. 72
c. 111
d. 114

Answer 1

find the common difference first

\[A_{27} = A_1 + (n - 1)d\] \[66 = -12 + (28 - 1)d\]

Answer 2

ok then what next

Answer 3

find d

Answer 4

how do I do that

Answer 5

\[66 = 12+ 27d\] isolate d

Answer 6

I tried but i never get a whole number

Answer 7

someone please help

Answer 8

what did you get?

Answer 9

2.8

Answer 10

\[66 - 12 = 27d\] \[54 = 27d\]

Answer 11

try that...that becomes whole

Answer 12

but it was already a -12 so don't you add them

Answer 13

it was originally \[66 = 12 + 27d\] i subtracted 12 from both sides \[66 - 12 = 27d\]

Answer 14

where did you get the 12 from?

Answer 15

ugh...i messed up my equation =_= should be \[66 = -12 + (27 - 1)d\] because there are 27 terms *facepalm* sorry

Answer 16

Thats ok that what i am confused on thats how I got 2.8

Answer 17

\[66 = -12 + 26d\] \[66 + 12 = 26d\] you should get a whole number now

Answer 18

ok I got 3

Answer 19

so common denominator is 3... now we solve for 42nd term

\[A_{42} = A_1 + (n - 1)d\]

Answer 20

a1 would be -12
n would be 42
d would be 3

Answer 21

so it would be 111

Answer 22

yup

Answer 23

thanks!