Question

find the 9th term the end ( towards the first term) of the ap:5,9,13,185.​

Answer 1

Answer:

$an = a + (n - 1)d \\ 185 = 5 + (n - 1)4 \\ 185 - 5 = (n - 1)4 \\ \frac{180 }{4} = n - 1 \\ 45 + 1 = n \\ n = 46$

$a9 = a + 8d \\ = 5 + 8 \times 4 \\ = 5 + 32 \\ = 37$

ok