f(x) = 3x2 + 18x + 32the function will have a least value if f''(x) is greater tan zero ie f'(x)>0 f'(x) = 6x + 18f''(x) = 6 Since f''(x)>0,The function has a least value at the turning point, gradient, i.e., f'(x) = 6x + 18 = 06x + 18 = 06x = -18x = -618x = -3Put x = -3 into f(x) to determine the least value 3(-3)2 + 18(-3) + 323(9) - 54 + 3227 - 54 + 32 = 5