Question

Find the 64th term of the arithmetic sequence -4, -21, -38, ...−4,−21,−38,

Answer 1

$a_{n} = a_{1} + d(n - 1)$  ; a₁ is the first term, d is the difference between terms, and n is the term

-4, -21, -38, ...   ⇒   a₁ = -4, d = -17

$a_{n} = -4 - 17(n - 1)$

   = -4 - 17n + 17

   = 13 - 17n

$a_{64} = 13 - 17(64)$

    = 13 - 1088

    = 1075

Answer: 1075