f'=-3(-3)/(2-3x)^4
f"=-36/(2-3x)^5
now look at f', and f" at each side of 2/3, say at .5, and at 1.0
I will do the 1.0 side...
f=1/(2-3)^3=1
f'=9/(2-3)^4= positive 9, high slope
f"=-36/(2-3)^5=36 positive, curving up
now the .5 side.
f=1/(2-1.5)^3=8
f'=9/(2-1.5)^4=9*64 positive, going upwards
f"=-36/(.5)^5=-1152 negative curving down,slope is reducing.
Now graph it on your calculator and take a look