The fourth term of an arithmetic sequence is 3, and the ninth term is 23. What is the first term of this sequence? What is the sum of the first ten terms of this sequence?
3==F + 3D,
23==F + 8D, solve for F, D
Use substitution to get:
F== - 9 - this is the first term
D== 4 - this is the common difference.
Your sequence looks like this:
-9 , -5 , -1 , 3 , 7 , 11 , 15 , 19 , 23 , 27 , >>Number of terms = 10>>Total Sum == 90
