a: \(12x^3-6x^2+3x\)

\(=3x\cdot4x^2-3x\cdot2x+3x\cdot1\)

\(=3x\left(4x^2-2x+1\right)\)

b: \(\dfrac{2}{5}x^2+5x^3+x^2y\)

\(=x^2\cdot\dfrac{2}{5}+x^2\cdot5x+x^2\cdot y\)

\(=x^2\left(\dfrac{2}{5}+5x+y\right)\)

c: \(14x^2y-21xy^2+28x^2y^2\)

\(=7xy\cdot2x-7xy\cdot3y+7xy\cdot4xy\)

\(=7xy\left(2x-3y+4xy\right)\)

\(12x-9-4x^2=-\left(2x-3\right)^2\\ Sửa:x^3-6x^2y+12xy^2-8y^3=\left(x-2y\right)^3\)

\(a.6x^3-9x^2=3x^2\left(2x-3\right)\\ b.20x^2y-12x^3=4x^2\left(5y-3x\right)\)

a) \(6x^3-9x^2=3x^2\left(2x-3\right)\)

b) \(20x^2y-12x^3=4x^2\left(5y-3x\right)\)

3x³ + 6x²y+ 3xy²

=3x³ + 3x²y + 3x²y + 3xy²

= 3x²(x +y) + 3xy(x +y)

=(x+y)(3x² + 3xy)

= 3x(x+y)(x+y)

= 3x(x+y)²

đề dài nên T giải câu a thôi bn tự làm tiếp mấy câu khác nhé 

2x^2 - 2y^2 - 6x - 6y 

= 2(x^2-y^2) - 6(x+ y) 

= 2(x-y)(x+y) - 6(x+y) 

= (2(x-y)-6) (x+y)

ko biết

a) \(=3\left(5y+4x\right)\)

b) \(=\left(x-3\right)^2\)

c) \(=y\left(y^2+2y+3\right)\)

4x^2 + 12x +9

= (2x)^2 + 2.2x.3 + 3^2

= ( 2x +3 ) ^2

x^2 - 2x - 15 

= x^2 - 5x + 3x - 15

= ( x^2 + 3x ) - (5x +15 )

= x ( x +3 ) - 5 ( x + 3 )

(x + 3 ) ( x - 5 )

\(4x^4y-4x^2y^3+12x^3y+12x^2y^2\)

\(=4x^2y\left(x^2-y^2+3x+3y\right)\)

\(=4x^2y\left(x-y-3\right)\left(x+y\right)\)

a)  \(27x^3-8=\left(3x-2\right)\left(9x^2+6x+4\right)\)

b)  \(8x^3+12x^2+6x+1=\left(2x+1\right)^3\)

c)  \(\left(2y-1\right)^1-4x^2+4x-1=\left(2y-1\right)^2-\left(2x-1\right)^2=\left(2y-1-2x+1\right)\left(2y-1+2x-1\right)\)

\(=\left(2y-2x\right)\left(2y+2x-2\right)=4\left(y-x\right)\left(y+x-1\right)\)