Question

Find the 9th term of the arithmetic sequence.

a7 = -42 and a11 = -28; a9 = ____.

Answer 1

so a really simple solution to this is to find the average of the 7th and 11th term, the average will be the 9th term

(-42 + (-28))/2 =

Answer 2

-35?

Answer 3

the reason for using this method is to recognise that

(7 + 11)/2 = 9

so the average of the 2 terms is the 9th term

a quick and dirty solution

Answer 4

-35 is correct

Answer 5

thanks