(2*a + b)*(c - a) + (b + c)*(a + b)
(a + b)*(b + c) + (b + 2.0*a)*(c - a)
(a + b)*(b + c) - (a - c)*(b + 2*a)
2 2 b - 2*a + 2*b*c + 3*a*c