Answer:
y = 108x + 216
Step-by-step explanation:
given
y = 4x³ then
= 12x² = 
x = 3 ⇒ m = 12(- 3)² = 108
equation of tangent in slope- intercept form is
y = mx + b ( m is the slope and b the y- intercept ), hence
y = 108x + b
To find b substitute (- 3, - 108) into the equation
- 108 = -324 + b ⇒ b = - 108 + 324 = 216
y = 108x + 216 ← equation of tangent