x²-xy-2y²

= x²-2xy+xy-2y²

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

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

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

\(=x\left(y-1\right)+y\left(y-1\right)-x^2\left(y^2-1\right)\)\(=\left(y-1\right)\left[x+y-x^2\left(y+1\right)\right]\)

\(=\left(y-1\right)\left(x+y-x^2y-x^2\right)\)\(=\left(y-1\right)\left[x\left(1-x\right)+y\left(1-x^2\right)\right]\)

\(=\left(y-1\right)\left(1-x\right)\left[x+y\left(1+x\right)\right]=\left(y-1\right)\left(1-x\right)\left(xy+x+y\right)\)

a/ \(=2xy+x^2-2y^2-xy=x\left(2y+x\right)-y\left(2y+x\right)=\left(x-y\right)\left(2y+x\right)\)

b/ \(=x^2-3xy-2y^2\)

c/ \(=2xy-6y^2+x^2-3xy=2y\left(x-3y\right)+x\left(x-3y\right)=\left(2y+x\right)\left(x-3y\right)\)

d/ \(=xy-2y^2+2x^2-4xy=y\left(x-2y\right)+2x\left(x-2y\right)=\left(y+2x\right)\left(x-2y\right)\)

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

b) nghiệm lẻ>mìh nghĩ là sai đề

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

d)(x-2y)(2x+y)
 

____________________________
li-ke cho mk nha bnLe Ngoc Bao Chau
 

x^2 + xy - 2y^2 = ( x^2 - 2xy + y^2 ) + 3xy - 3y^2 = ( x - y )^2 + 3y.( x - y ) = ( x - y )(x + 2y)

5x²+14x-3=(5x²+15x)-(x+3)=5x(x+3)-(x+3)=(x+3)(5x-1)

5x²-18x-8=(5x²-20x)+(2x-8)=5x(x-4)+2(x-4)=(x-4)(5x+2)

6x²+7x-3=(6x²-2x)+(9x-3)=2x(3x-1)+3(3x-1)=(3x-1)(2x+3)

x²-xy-2y²=(x²-y²)-(xy+y²)=(x-y)(x+y)-y(x+y)=(x+y)(x-y-y)=(x+y)(x-2y)

a, = (xy-y^2) + (2x-2y) = y(x-y) + 2.(x-y) = (x-y).(y+2) 

b, = (x+y)^2 - 9 = (x+y-3).(x+y+3)

\(xy-y^2-2x-2y\)   

=(xy-y).(2x-2y)

=y(x-y).2(x-y)

=(x-y).(y-2)

camr ơn bạn nha