The formula for a tangent line is:
y - f(a) = f’(a) (x-a)
In our case we are given the point (3, f(3)).
We know f(3) = 16, f’(3) = 3 [the slope at said x value].
Now plug it in:
y - f(3) = f’(3) (x-3)
y -16 = 3 * (x - 3)
y = 3x +16 -9
y = 3x + 7
Tangent Line^
Feel free to correct me if something is off. Hope this helps.