Find an explicit formula for the geometric sequence β 9 β , β 18 β , β 36 β , β 72 , . . . β9,β18,β36,β72,...minus, 9, comma, minus, 18, comma, minus, 36, comma, minus, 72, comma, point, point, point. c ( n ) = c(n)=c, left parenthesis, n, right parenthesis, equals