Find the derivative of f(x) = -12x2 + 9x at x = 6.
a) -112.5
b)-135
c)90
d)108

hi

f(x) = -12x²+9x

So

f'(x) =  -24x +9

if  x = 6   then  f'(6) = -24 (6) +9 = -135

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