Question

Which of these is a tangent line to y= -x^2 at x=4

Answer 1

Explanation:

an equation of this tangent is : y = f'(4)(x-a)+f(4)

a = f'(4)

f(x) = - x²

a=4

f'(x) = -2x

f'(4) = -2(4) = -8

f(4) = -(4)² = -16

so : y = - 8 (x-4)-16

y = - 8x +16