A = abc - (ab + bc + ca) + a + b + c - 1

= (abc - ab) - (bc - b) - (ac - a) + (c - 1)

= ab(c - 1) - b(c - 1) - a(c - 1) + (c - 1) 

= (ab - b - a + 1)(c - 1) 

= (a - 1).(b - 1).(c - 1)   

$A=8abc+4\left(ab+bc+ca\right)+2\left(a+b+c\right)+1$

A = 8abc + 4ab + 4bc + 4ca + 2a + 2b + 2c + 1

$A=\left(8abc+4ab\right)+\left(4bc+2b\right)+\left(4ca+2a\right)+\left(2c+1\right)$

$A=4ab\left(2c+1\right)+2b\left(2c+1\right)+2a\left(2c+1\right)+\left(2c+1\right)$

$A=\left(2c+1\right)\left(4ab+2a+2b+1\right)$

$A=\left(2c+1\right)\left[2a\left(2b+1\right)+\left(2b+1\right)\right]$

$A=\left(2a+1\right)\left(2b+1\right)\left(2c+1\right)$

a: =(x+y)^3+z^3-3xy(x+y)-3xyz

\(=\left(x+y+z\right)\left[\left(x+y\right)^2-z\left(x+y\right)+z^2\right]-3xy\left(x+y+z\right)\)

\(=\left(x+y+z\right)\left(x^2+2xy+y^2-xz-yz+z^2-3xy\right)\)

\(=\left(x+y+z\right)\left(x^2+y^2+z^2-xy-xz-yz\right)\)

b: \(=\left(x+y+y-z\right)^3-3\left(x+y\right)\left(y-z\right)\left(x+y+y-z\right)+\left(z-x\right)^3\)

\(=\left(x-z\right)^3+\left(z-x\right)^3-3\left(x+y\right)\left(y-z\right)\left(x-z\right)\)

\(=-3\left(x+y\right)\left(y-z\right)\left(x-z\right)\)

c: \(=\left(x^2+x\right)^2+3\left(x^2+x\right)+2-12\)

\(=\left(x^2+x\right)^2+3\left(x^2+x\right)-10\)

=(x^2+x+5)(x^2+x-2)

=(x^2+x+5)(x+2)(x-1)

d: =b^2c+bc^2+ac^2-a^2c-a^2b-ab^2

=b^2c-b^2a+bc^2-a^2b+ac^2-a^2c

=b^2(c-a)+b(c^2-a^2)+ac(c-a)

=(c-a)(b^2+ac)+b(c-a)(c+a)

=(c-a)(b^2+ac+bc+ba)

=(c-a)[b^2+bc+ac+ab]

=(c-a)[b(b+c)+a(b+c)]

=(c-a)(b+c)(b+a)

\(a,=x\left(2x-y\right)+\left(2x-y\right)=\left(x+1\right)\left(2x-y\right)\\ b,=\left(a+b\right)\left(c-2\right)\\ c,=x\left(x+4y\right)+2\left(x+4y\right)=\left(x+2\right)\left(x+4y\right)\\ d,=x\left(x+2y\right)+3\left(x+2y\right)=\left(x+3\right)\left(x+2y\right)\)

\(=a^2b-ab^2+b^2c-bc^2+ac^2-a^2c\)

\(=a^2\left(b-c\right)+bc\left(b-c\right)-a\left(b-c\right)\left(b+c\right)\)

\(=\left(b-c\right)\left(a^2-bc-ab-ac\right)\)

\(=\left(b-c\right)\left[a\left(a-b\right)-c\left(a-b\right)\right]\)

\(ab\left(b-a\right)-bc\left(b-c\right)-ac\left(c-a\right)\)

\(=ab\left(b-a\right)-b^2c+bc^2-ac^2+a^2c\)

\(=ab\left(b-a\right)+c^2\left(b-a\right)-c\left(b^2-a^2\right)\)

\(=\left(b-a\right)\left(ab+c^2-bc-ca\right)\)

\(=\left(b-a\right)\left[b\left(a-c\right)-c\left(a-c\right)\right]\)

\(=\left(b-a\right)\left(a-c\right)\left(b-c\right)\)

nhân hả bạn

ab(b - a) - bc(b - c) - ac(c - a)

= ab² - a²b - b²c +  bc² + ac(a - c)

= b²(a - c) - b(a² - c²) + ac(a - c)

= b²(a - c) - b(a - c)(a + c) + ac(a - c)

= (b² - ab - bc + ac)(a - c)

= [b(b - a) - c(b - a)](a - c)

= (b - c)(b -a)(a - c)

\(ab\left(b-a\right)-bc\left(b-c\right)-ac\left(c-a\right)\)

\(=ab\left(b-a\right)-\left(b^2c-bc^2\right)-\left(ac^2-a^2c\right)\)

\(=ab\left(b-a\right)-b^2c+bc^2-ac^2+a^2c\)

\(=ab\left(b-a\right)-\left(b^2c-a^2c\right)+\left(bc^2-ac^2\right)\)

\(=ab\left(b-a\right)-c\left(b^2-a^2\right)+c^2\left(b-a\right)\)

\(=ab\left(b-a\right)-c\left(b-a\right)\left(b+a\right)+c^2\left(b-a\right)\)

\(=\left(b-a\right)\left[ab-c\left(b+a\right)+c^2\right]=\left(b-a\right)\left[ab-\left(bc+ac\right)+c^2\right]\)

\(=\left(b-a\right)\left(ab-bc-ac+c^2\right)=\left(b-a\right)\left[\left(ab-bc\right)-\left(ac-c^2\right)\right]\)

\(=\left(b-a\right)\left[b\left(a-c\right)-c\left(a-c\right)\right]=\left(b-a\right)\left(b-c\right)\left(a-c\right)\)