Complete the recursive formula of the arithmetic sequence 9, -1, -11, -21,...9,−1,−11,−21,...9, comma, minus, 1, comma, minus, 11, comma, minus, 21, comma, point, point, point. d(1)=d(1)=d, left parenthesis, 1, right parenthesis, equals
d(n)=d(n-1)+d(n)=d(n−1)+d, left parenthesis, n, right parenthesis, equals, d, left parenthesis, n, minus, 1, right parenthesis, plus