Answer:
1) increasing on (-∞,-1] ∪ [1,∞), decreasing on [-1,0) ∪ (0,1]
is local maximum,
is local minimum
2) increasing on [1,∞), decreasing on (-∞,0) ∪ (0,1]
is absolute minimum
3) increasing on (-∞,0] ∪ [8,∞), decreasing on [0,4) ∪ (4,8]
is local maximum,
is local minimum
4) increasing on [2,∞), decreasing on (-∞,2]
is absolute minimum
5) increasing on the interval (0,4/9], decreasing on the interval [4/9,∞)
is local minimum,
is absolute maximum
Step-by-step explanation:
To find minima and maxima the of the function, we must take the derivative and equalize it to zero to find the roots.
1) ![f(x) = 6x + 6/x](https://tex.z-dn.net/?f=f%28x%29%20%3D%206x%20%2B%206%2Fx)
and ![x \neq 0](https://tex.z-dn.net/?f=x%20%5Cneq%200)
So, the roots are
and ![x = 1](https://tex.z-dn.net/?f=x%20%3D%201)
The function is increasing on the interval (-∞,-1] ∪ [1,∞)
The function is decreasing on the interval [-1,0) ∪ (0,1]
is local maximum,
is local minimum.
2) ![f(x)=6-4/x+2/x^2](https://tex.z-dn.net/?f=f%28x%29%3D6-4%2Fx%2B2%2Fx%5E2)
and ![x \neq 0](https://tex.z-dn.net/?f=x%20%5Cneq%200)
So the root is ![x = 1](https://tex.z-dn.net/?f=x%20%3D%201)
The function is increasing on the interval [1,∞)
The function is decreasing on the interval (-∞,0) ∪ (0,1]
is absolute minimum.
3) ![f(x) = 8x^2/(x-4)](https://tex.z-dn.net/?f=f%28x%29%20%3D%208x%5E2%2F%28x-4%29)
and ![x \neq 4](https://tex.z-dn.net/?f=x%20%5Cneq%204)
So the roots are
and ![x = 8](https://tex.z-dn.net/?f=x%20%3D%208)
The function is increasing on the interval (-∞,0] ∪ [8,∞)
The function is decreasing on the interval [0,4) ∪ (4,8]
is local maximum,
is local minimum.
4) ![f(x)=6(x-2)^{2/3} +4=0](https://tex.z-dn.net/?f=f%28x%29%3D6%28x-2%29%5E%7B2%2F3%7D%20%2B4%3D0)
has no solution and
is crtitical point.
The function is increasing on the interval [2,∞)
The function is decreasing on the interval (-∞,2]
is absolute minimum.
5)
for ![x>0](https://tex.z-dn.net/?f=x%3E0)
![f\prime(x) = (4/\sqrt x)-6 = 0](https://tex.z-dn.net/?f=f%5Cprime%28x%29%20%3D%20%284%2F%5Csqrt%20x%29-6%20%3D%200)
So the root is ![x = 4/9](https://tex.z-dn.net/?f=x%20%3D%204%2F9)
The function is increasing on the interval (0,4/9]
The function is decreasing on the interval [4/9,∞)
is local minimum,
is absolute maximum.