Write integral subscript short dash 1 end subscript superscript 2 left parenthesis x squared plus 2 right parenthesis d x as the limit of a Riemann sum and evaluate. a.) limit as n rightwards arrow infinity of sum from space k equals 1 to n of open parentheses 3 minus fraction numerator 6 k over denominator n end fraction plus fraction numerator 9 k squared over denominator n squared end fraction close parentheses open parentheses 3 over n close parentheses equals 9 b.) limit as n rightwards arrow infinity of sum from space k equals 1 to n of open parentheses short dash 1 plus fraction numerator 3 k over denominator n end fraction close parentheses open parentheses 3 over n close parentheses equals 3 over 2 c.) limit as n rightwards arrow infinity of sum from space k equals 1 to n of open parentheses 3 plus fraction numerator 6 k over denominator n end fraction plus fraction numerator 9 k squared over denominator n squared end fraction close parentheses open parentheses 3 over n close parentheses equals 13 over 3 d.) limit as n rightwards arrow infinity of sum from space k equals 1 to n of open parentheses 3 plus fraction numerator 9 k squared over denominator n squared end fraction close parentheses open parentheses 3 over n close parentheses equals 18