Find the open interval(s) on which f(x) = -2x + 12x+8 is increasing or decreasing.increasing on (??,6); decreasing on (6,?)increasing on (-?,16); decreasing on (16,?)increasing

Find the open interval(s) on which f(x) = -2x² + 12x+8 is increasing or decreasing.increasing on (??,6); decreasing on (6,?)increasing on (-?,16); decreasing on (16,?)increasing on (-?, 32); decreasing on (32,?)increasing on (-?, 24); decreasing on (24,?)increasing on (-?,3); decreasing on (3,?)