[tex]a_{n} = a_{1} + d(n - 1)[/tex] ; a₁ is the first term, d is the difference between terms, and n is the term
-4, -21, -38, ... ⇒ a₁ = -4, d = -17
[tex]a_{n} = -4 - 17(n - 1)[/tex]
= -4 - 17n + 17
= 13 - 17n
[tex]a_{64} = 13 - 17(64)[/tex]
= 13 - 1088
= -1075
Answer: -1075
