First: your notation is only clear because you have specified that f passes through (2,2); otherwise the denominator is equivocal. You should use sqrt(...) to make clear what is under the radical sign.
f'(x) = 4 (-1/2) (3x-2)-3/2 3 = -6/sqrt[(3x-2)3]
f'(2) = -6/sqrt(64) = -3/4