-c2(a - b) + b2(a - c) - a2(b - c)
= -c2a + c2b + b2a - b2c - a2b + a2c
= (a2c - c2a + c2b - b2c) + (b2a - a2b)
= c(a2 - ac + bc - b2) + ab(b - a)
= c2[(a - b)(a + b) - c(a - b)] - ab(a - b)
= c2(a - b)(a + b - c) - ab(a - b)
= (a - b)(c2a + c2b - c3 - ab)