2(a-1)方-12(a-1)+18
=2[(a-1)^2-6(a-1)+9)]
=2(a-1-3)^2
=2(a-4)^2
-a方-b方+c方+2ab
=-(a^2+b^2-2ab-c^2)
=-[(a-b)^2-c^2]
=-(a-b+c)(a-b-c)
2(a-1)方-12(a-1)+18
=2[(a-1)^2-6(a-1)+9)]
=2(a-1-3)^2
=2(a-4)^2
-a方-b方+c方+2ab
=-(a^2+b^2-2ab-c^2)
=-[(a-b)^2-c^2]
=-(a-b+c)(a-b-c)