A=9b^2c-3bc^2-9ac^2-3a^2c-9a^2b-3a^2+28abc

A=9.(b^2c-ac^2-a^2.b)-3.(bc^2+a^2.c+3a^2)+28abc

A=9.(b.(bc-a^2)-ac^2)-3.(c.(bc+a^2)+3a^2)+28abc

k dung mik nhe!!!!!

\(a^3-b^3+c^3+3abc\)

\(=\left(a-b\right)^3+c^3+3abc+3a^2b-3ab^2\)

\(=\left[\left(a-b\right)^3+c^3\right]+3ab\left(c+a-b\right)\)

\(=\left(c+a-b\right)\left[\left(a-b\right)^2-\left(a-b\right)c+c^2\right]+3ab\left(c+a-b\right)\)

\(=\left(c+a-b\right)\left(a^2-2ab+b^2-ac+bc+c^2+3ab\right)\)

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

a) 4x² - 1
= (2x - 1)(2x + 1)

b) ax + 3a - bx - 3b
= a(x + 3) - b(x + 3)
= (x + 3)(a - b)

c) 4x² - 8xy + 4y² - 16
= (2x - 2y)² - 4²
= (2x - 2y - 4)(2x - 2y + 4)

d) 2x² - 3x - 9
= 2x² + 3x - 6x - 9
= x(2x + 3) - 3(2x + 3)
= (2x + 3)(x - 3)

a) x²+x-2
= x²-x+2x-2
= x(x-1)+2(x-1)
= (x+2)(x-1)
b) 2x²+5x+3
= 2x²+2x+3x+3
= 2x(x+1)+3(x+1)
= (2x+3)(x+1)
c) 3x²+5x-2
= 3x²+6x-1x-2
= 3x(x+2)-1(x+2)
= (3x-1)(x+2)

\(abc-\left(ab+bc+ac\right)+\left(a+b+c\right)-1=\left(abc-ab\right)-\left(bc-b\right)-\left(ac-a\right)+\left(c-1\right)=ab\left(c-1\right)-b\left(c-1\right)-a\left(c-1\right)+\left(c-1\right)=\left(c-1\right)\left(ab-b-a+1\right)=\left(c-1\right)\left[b\left(a-1\right)-\left(a-1\right)\right]=\left(a-1\right)\left(b-1\right)\left(c-1\right)\)

\(=4ab\left(ab+ax+bx+x^2\right)=4a^2b^2+4a^2bx+4ab^2x+4abx^2\)

4ab(a + x)(b + x) là nhân tử rồi nhé

\(\left(ab-1\right)^2+\left(a+b\right)^2=a^2b^2-2ab+1+a^2+2ab+b^2=a^2+b^2+a^2b^2+1=a^2\left(b^2+1\right)+\left(b^2+1\right)=\left(a^2+1\right)\left(b^2+1\right)\)

\(\left(ab-1\right)^2+\left(a+b\right)^2=a^2b^2-2ab+1+a^2+2ab+b^2=a^2b^2+a^2+b^2+1=\left(a^2b^2+a^2\right)+\left(b^2+1\right)=a^2\left(b^2+1\right)+\left(b^2+1\right)=\left(a^2+1\right)\left(b^2+1\right)\)

\(\left(ab-1\right)^2+\left(a+b\right)^2\)

\(=a^2b^2+1+a^2+b^2\)

\(=\left(a^2+1\right)\left(b^2+1\right)\)

=abc-ab-bc-ca+a+b+c-1

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

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

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

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

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