Answer:
x = 3
Step-by-step explanation:
f'(x) = 0 for x = 3 and x = 4 . . . . by the zero product rule.
The coefficient of x² in f'(x) is negative, so the parabola opens downward.
f''(x) is positive for x < 3.5, so the coordinate x = 3 represents a relative minimum.
