Okay, I am assuming that [tex] a_{1} [/tex] is equal to [tex] t_{1} [/tex]
Formula:
[tex] a_{n} = a_{1} + (n -1) d[/tex]
Substitute:
n for 9
[tex] a_{1} [/tex] for 10
d for [tex] -\frac{1}{2} [/tex]
Solution:
[tex] a_{9} [/tex] = 10 + ( 9 -1)[tex]- \frac{1}{2} [/tex]
[tex] a_{9} [/tex] = 10 + 8 ([tex]- \frac{1}{2} [/tex])
[tex] a_{9} [/tex] = 10 + -4
[tex] a_{9} [/tex] = 10 - 4
[tex] a_{9} [/tex] = 6
Check:
First 9 terms: 10, 9.5, 9, 8.5, 8, 7.5, 7, 6.5, 6
Answer:
The 9th term is 6.
