Question 1169395
In this arithmetic sequence wee are given that S1=9 AND S2=20
What is the 4th terms.
Thanks for your help.
<pre>2 of them are WRONG!!
{{{matrix(1,3, S[1], "=", 9)}}}
If the sum of ONE (1) number in the sequence is 9, then that means that the 1st term , or {{{matrix(1,3, a[1], "=", 9)}}}
{{{matrix(1,3, S[2], "=", 20)}}}
If the sum of TWO (2) numbers in the sequence is 20, then that means that the 2nd term, or {{{matrix(1,5, a[2], "=", 20 - 9, "=", 11)}}}
Therefore, the common difference (d) is: 2 (11 - 9)
With each term, or a<sub><b>n</sub></b> = a<sub><b>1</sub></b> + (n - 1)d, then the 4th term, or {{{highlight_green(matrix(1,7, a[4], "=", 9 + (4 - 1)2, "=", 9 + 6, "=", highlight(15)))}}}, or Just SIMPLY add 2(2), or 4 to the 2nd term, 11.