1.(3a+2b)(-3a-2b)=-(3a+2b)(3a+2b)=-(3a+2b)²
2.(0.5+b/3)²=(1/2+b/3)²=(3+2b)²/36
3.(-8b+1/4)²=(8b-1/4)²=(32b-1)²/16