Question

Is `f(x)=(x-2)(x+1)(x+4)` increasing or decreasing at `x=1`?

Answer 1

`f'(1)=3>0`

Explanation:

By differentiating with respect to `x` we get

`f'(x)=(x+1)(x+4)+(x-2)(x+4)+(x-2)(x+1)`
simplifying this we get

`f'(x)=3x^2+6x-6`
`f'(1)=3>0`