a²+b²(a-b)+b+2c+2(b-c)+c²+2a+2(c-a)

đề thế này hả bạn

(ab-1)²-(a-2)²

=(ab-1-a+2)(ab-1+a-2)

=(ab-a+1)(ab+a-3)

c)x⁴-2x³-6x-9

=(x4-9)-(2x3+6x)

=(x²+3)(x²-3)-2x(x²-3)

=(x²-3)(x²+3-2x)

a³ +b³ + c³ -3abc

=a³+3a²b+3ab²+b³+c³-3a²b-3ab²-3abc

=(a³+3a²b+3ab²+b³)+c³-(3a²b+3ab²+3abc)

=(a+b)³+c³-3ab(a+b+c)

=(a+b+c)[(a+b)²-(a+b)c+c²)]-3ab(a+b+c)

=(a+b+c)[a²+2ab+b²-(ac+bc)+c²]-3ab(a+b+c)

=(a+b+c)(a²+2ab+b²-ac-bc+c²-3ab)

=(a+b+c)(a²+b²+c²-ac-bc-ab)