Let f (x) = X +51 . Find the critical points c that correspond to local minima. Use symbolic notation and fractions where needed. Give your answer in the form of a comma separated list. Enter DNE if there are no critical points.) Find the critical points c that correspond to local maxima. (Use symbolic notation and fractions where needed. Give your answer in the form of a comma separated list. Enter DNE if there are no critical points.) Find the values at which the points of inflection occur. (Use symbolic notation and fractions where needed, Give your answer in the form of a comma separated list. Enter DNE if there are no inflection points.) Determine the interval on which f is concave up. (Use symbolic notation and fractions where needed. Give your answer as interval in the form (*, *). Use the symbol . for infinity, U for combining intervals, and an appropriate type of parenthesis "(",")", "[", "]" depending on whether the interval is open or closed. Enter ( if the interval is empty.) XE