-(b-2)(3-4b)
(b+2)(3-2b)
(b-4)^2

-(b-2)(3-4b)=-(3b-4b²-6+8b)=-3b+4b²+6-8b=4b²-11b+6(b+2)(3-2b)=3b-4b²+6-4b=-4b²-b+6(b-4)²=b²-8b+16