Answer:
Decreasing (2, 6); increasing on (-∞, 2) U (6, ∞)
Step-by-step explanation:
To determine where [tex]f(x)[/tex] is increasing or decreasing, we set [tex]f'(x)=0[/tex] and check for the intervals.
We see that [tex]f'(x)=0[/tex] when either [tex]x=2[/tex] or [tex]x=6[/tex]. Therefore, we'll need to check the intervals [tex](-\infty,2)[/tex], [tex](2,6)[/tex], and [tex](6,\infty)[/tex]
For the interval [tex](\infty,2)[/tex], we can pick [tex]x=0[/tex] . This means that[tex]f'(0)=(2-0)(6-0)=(2)(6)=12>0[/tex], showing that [tex]f(x)[/tex] increases on the interval [tex](-\infty,2)[/tex]
For the interval [tex](2,6)[/tex], we can pick [tex]x=4[/tex]. This means that [tex]f'(4)=(2-4)(6-4)=(-2)(2)=-4<0[/tex], showing that [tex]f(x)[/tex] decreases on the interval [tex](2,6)[/tex]
For the interval [tex](6,\infty)[/tex], we can pick [tex]x=7[/tex]. This means that [tex]f'(7)=(2-7)(6-7)=(-5)(-1)=5>0[/tex], showing that [tex]f(x)[/tex] increases on the interval [tex](6,\infty)[/tex]
Therefore, [tex]f(x)[/tex] is increasing on [tex](-\infty,2)\cup(6,\infty)[/tex] and is decreasing on [tex](2,6)[/tex].
