Mark M. answered 12/08/19
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
y = (e4x - 4)2
y' = 2(e4x - 4)(e4x - 4)' = 2(e4x - 4)(4e4x)
At the point (0,9), y' = 2(-3)(4) = -24
Equation of tangent line at (0,9): y - 9 = -24(x - 0)
y = -24x + 9