a) =a(b2- c2) + bc2- ba2 +a2c - b2c
=a(b2-c2) - (b2c - bc2) - (ba2 - a2c)
=a(b-c)(b+c) -bc(b-c) - a2(b-c)
=(b-c)\(\left[a\left(b+c\right)-bc-a^2\right]\)
=(b-c)(ab+ac-bc-a2)
=\(\left(b-c\right)\left[\left(ab-bc\right)-\left(a^2-ac\right)\right]\)
=\(\left(b-c\right)\left[b\left(a-c\right)-a\left(a-c\right)\right]\)
=\(\left(b-c\right)\left(a-c\right)\left(b-a\right)\)