bài 2A=a−bc+b−ca+c−ab=a2−ab2+b2c−bc2+c2a−ca2abc
PTĐT thành nhân tử => A=(a−b)(a−c)(b−c)abc
B=ca−b+ab−c+cc−a=bc2−abc−c3+ac2+a2c−a3−abc+a2b+ab2−b3−abc+b2(a−b)(b−c)(c−a)=a3+b3+c3−a2b−ab2−b2c−bc2−a2c−ac2+3abc(a−b)(a−c)(b−c)
Tử thức =(a+b)3+c3−4a2b−4ab2−bc−bc2−ac−ac2+3abc=(a+b+c)((a+b)2−(a+b)c+c2)−4ab(a+b)−bc(b+c)−ac(a+c)+3abc
Vì a+b+c=0=>{a+b=−ca+c=−bb+c=−a
=>B=9abc(a−b)(a−c)(b−c)
=> P=A.B=9