Question

write an A.P whose first term is 9 and common difference is -5​

Answer 1

$\huge\bold\green{ solution }$

given;

first term = 9

common difference = -5

proof;

$tn = a + (n - 1)d \\ \\ tn = 9 + (n - 1) - 5 \\ \\ tn = 9 + - 5n + 5 \\ \\ tn = 14 - 5n$

$- 5n = 14 \\ \\ n = \frac{ - 14}{5} \\ \\ n = 2.8$