Question

(a-b+c) (a+b-c) gives what?

Answer 1

(a-b+c) (a+b-c) will give
=a^2+ab-ac-ab-b^2+bc+ac+cb-c^2
=a^2-b^2-c^2+2bc
Or
a^2-(b^2+c^2-2bc)
=a^2-(b-c)^2
=a^2-(b-c)(b-c)