Question

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

Answer 1

decreasing at x = 1

Explanation:

To determine if a function is increasing/decreasing at x = a , require to find the value of f'(a).

• If f'(a) > 0 ,then f(x) is increasing at x = a

• If f'(a) < 0 , then f(x) is decreasing at x = a

now `f'(x) = -8x + 1`

and f'(1) = -8 + 1 = -7

since f'(1) < 0 , then f(x) is decreasing at x = 1
graph{-4x^2+x-1 [-10, 10, -5, 5]}