Basic Algebra + basic calculus/ find the equation of a line

Find the equation of the line tangent to the graph of $f$ at $(1, -3)$, where $f$ is given by $f(x) = 6x^3 − 13x^2 + 4$. Use $y$ as the dependent variable when you write your equation.

My answer which was false:

The $f'(x)= 18x^2-26x$
$f'(1) = 18-26 = -8$

the equation $(y+3)=-8(x-1)$
$y= -8x+5$

but it was false, so could any one help please :)