(3a+1)(3a-1)-(2a-3)(3a+2)其中a=负三分之一
=9a²-1-6a²+9a-4a+6
=3a²+5a+5
=3*(-1/3)²+5*(-1/3)+5
=1/3-5/3+5
=-4/3+5
=3又3分之2