Geometric Sequence: r = 1 4 r = 1 4 This is the form of a geometric sequence. a n = a 1 r n − 1 a n = a 1 r n - 1 Substitute in the values of a 1 = 64 a 1 = 64 and r = 1 4 r = 1 4 . a n = ( 64 ) ⋅ ( 1 4 ) n − 1 a n = ( 64 ) ⋅ ( 1 4 ) n - 1 Apply the product rule to 1 4 1 4 . a n = 64 ⋅ 1 n − 1 4 n − 1 a n = 64 ⋅ 1 n - 1 4 n - 1 One to any power is one. a n = 64 ⋅ 1 4 n − 1 a n = 64 ⋅ 1 4 n - 1 Multiply 64 64 by 1 4 n − 1 1 4 n - 1 . a n = 64 ( 1 4 n − 1 ) a n = 64 ( 1 4 n - 1 ) Simplify 64 1 4 n − 1 64 1 4 n - 1 . Tap for more steps... a n = 64 4 n − 1