-3/4ab+2/3a^2b+ab-a^2b-1/2ab-5/3a^2b
=-3/4ab+ab-1/2ab+2/3a^2b-a^2b-5/3a^2b
=ab(-3/4+1-1/2)+a^2b(2/3-1-5/3)
=ab(-3/4+4/4-2/4)+a^2b(2/3-1-5/3)
=-1/4ab-2a^2b