If f (x) = 1+ 8x, find f '(a) for a=3 and the equation of the tangent line to f (x) at x =a. 5x - 13 A f '( a ) = - - ; equation of the tangent" one is y= 4 4 4 - 4x + 13 B f ' ( a ) = - ; equation of the tangent line is y= - 5 5 4x + 13 C f '( a ) = UI / A ; equation of the tangent line is y = 5 D f'( a) =- - 5 -5x - 13 ; equation of the tangent line is y = 4 4