given f(x)=7-15x+(9x^2)-(x^3)

Write an equation of the line tangent to the graph of f at x=2.

i know i have to find the derivative and plug in 2 for x, giving me 9 as the slope, but since they dont give us a point, is the equation just

y-y1=9(x-x1) ?? or would it be y=9x??

please help. thanks!!