differentiation help

For f(x) = 12 - 4x + 2x^2, find the equations of the tangent and the normal at the point where x=-1 on the curve with the equation y=f(x)

so i put x in to get y so (-1,18)
i differentiated f(x) and i got 4x-4 so the gradient is 4

what do i do next i'm so confused

4x-4 is the derivative or "gradient function". You input the x-coordinate and it outputs the gradient. The gradient is not 4 here, what is it?

the gradient is -8?

the gradient is -8?