Question

Is `f(x)=(x+2)^2-4x^2-3x` increasing or decreasing at `x=-1`?

Answer 1

`f'(-1)` is increasing at `x=-1`

Explanation:

`color(white)(xx)f(x)=(x+2)^2-4x^2-3x`

`=>f(x)=x^2+4x+4-4x^2-3x`
`=>f(x)=-3x^2+x+4`

`=>f'(x)=-6x+1`

`=>f'(-1)=6+1`
`=>f'(-1)=7`
`=>f'(-1)>0`

so `f'(-1)` is increasing at `x=-1`