\(5x^2+3\left(x+y\right)-5y^2=5\left(x+y\right)\left(x-y\right)+3\left(x+y\right)=\left(x+y\right)\left[5\left(x-y\right)+3\right]\)

\(5x-5y-xy+y^2=\left(5x-5y\right)-\left(xy-y^2\right)=5\left(x-y\right)-y\left(x-y\right)=\left(x-y\right)\left(5-y\right)\)

\(a,=x^2-9-x^2+6x-9=6x-18\\ b,=\left(x-y\right)\left(x+y\right)-5\left(x-y\right)=\left(x+y-5\right)\left(x-y\right)\)

\(=\left(x-y\right)\left(x+y\right)-5\left(x-y\right)=\left(x-y\right)\left(x+y-5\right)\)

\(=\left(x-y\right)\left(x+y\right)-5\left(x-y\right)=\left(x+y-5\right)\left(x-y\right)\)

\(x^2-y^2-5x+5y=\left(x+y\right)\left(x-y\right)-5\left(x-y\right)=\left(x-y\right)\left(x+y-5\right)\)

a) = (x - 1)(5x - 3)

b) = x(x + y) - 5(x + y)

= (x + y)(x - 5)

c) = x(x - y) - y(x - y)

= (x - y)^2

d) = 2(x² + 2x + 1 - y²)

= 2[(x + 1)² - y²]

= 2(x - y + 1)(x + y + 1)

\(=\left(x-y\right)\left(x+y\right)+5\left(x-y\right)\)

\(=\left(x+y+5\right)\left(x-y\right)\)

Học tốt

Ta có : x² - y² - 5x - 5y

= ( x² - y² ) - ( 5x + 5y )

= ( x - y )( x + y ) - 5( x + y )

= ( x + y )( x - y - 5 )

cảm ơn bạn moon nhé bạn đã giúp mình rất rất nhiều ( nick trên cx là cảu mình )

Câu 1 đề sai rồi bạn ơi 

Câu 2/ 5(x² + 2xy + y² ) = 5(x +y )²

\(1,=\left(x-3\right)\left(x+3\right)\\ 2,=\left(x-y\right)\left(5+a\right)\\ 3,=\left(x+3\right)^2\\ 4,=\left(x-y\right)\left(10x+7y\right)\\ 5,=5\left(x-3y\right)\\ 6,=\left(x-y\right)^2-z^2=\left(x-y-z\right)\left(x-y+z\right)\)

bạn gõ lại công thức cho rõ đi, khó đọc quá