a, x(x-y)+2(x-y)=(x-y)(x+2)

b, \(x^2-6xy+9y^2=\left(x-3y\right)^2\)Thay x=16, y=2 có

                \(x^2-6xy+9y^2=\left(x-3y\right)^2=\left(16-2\cdot3\right)^2=10^2=100\)

\(P=x^2-6xy+9y^2=\left(x-3y\right)^2\)

(Áp dụng 7 hằng đẳng thức đáng nhớ)

c/ 3x-9xy-9y²+6y-1

=3x.(1-3y)-(1-6y+9y²)

=3x.(1-3y)-(1-3y)²

=(1-3y)[3x-(1-3y)]

=(1-3y)(3x-1+3y)

d/ x⁴+x²y²+y⁴

=x⁴+2x²y²+y⁴-x²y²

=(x²+y²)²-x²y²

=(x²-xy+y²)(x²+xy+y²)

dat y^2+y=z cho gon

\(z^2-9z+20=z^2-4z-5z+20=z\left(z-4\right)-5\left(z-4\right)=\left(z-4\right)\left(z-5\right)\)

\(thaylai:\left(y^2+y-4\right)\left(y^2+y-5\right)\)

thay hay thi "k" ko hay thi thoi 

c: =(x-3-2y)(x-3+2y)

Phân tích theo cách nhóm hạng tử nhé bạn ! 

a, xy + xz - 2y - 2z

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

= (x - 2)(y + x)

b, x² - 6xy + 9y² - 25z²

= (x - 3y)² - 25z²

= (x - 3y - 5z)(x - 3y + 5z) 

Ngoài ra bạn có thể hỏi mình để bổ sung kiến thức nâng cao !

\(49.\left(y-4\right)^2-9y^2-36y-36\)

\(=7^2\left(y-4\right)^2-\left(9y^2+36y+36\right)\)

\(=\left(7y-28\right)^2-\left(3y+6\right)^2\)

\(=\left(7y-28+3y+6\right).\left(7y-28-3y-6\right)\)

\(=\left(10y-22\right).\left(4y-34\right)\)

\(=4.\left(5y-11\right).\left(2y-17\right)\)

\(49\left(y-4\right)^2-9y^2-36y-36\)

\(=\) \(4\left(2y-17\right)\left(5y-11\right)\)

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

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

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

\(3x^4-48=3\left(x^4-16\right)=3\left[\left(x^2\right)^2-4^2\right]\\ =3\left(x^2-4\right)\left(x^2+4\right)\\ =3\left(x-2\right)\left(x+2\right)\left(x^2+4\right)\)

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