(-a-3b)(-a+3b)
=a²-9b²
(xy-1)²
=x²y²-2xy+1
﹙3分之2m-4分之1b﹚²
=9分之4m²-3分之mb+16分之b²
﹙-a-3﹚²
=[-(a+3)]²
=(a+3)²
=a²+6a+9