b: \(3x+3y-x^2-2xy-y^2\)

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

\(=\left(x+y\right)\left(3-x-y\right)\)

b) 3x+3y-x²-2xy-y²

=3(x+y)-(x+y)²

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

Chon D

D

\(x^2-2xy+5x-10y\)

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

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

\(x^2-2xy+5x-10y\)

\(=\left(x^2-2xy\right)+\left(5x-10y\right)\)

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

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

\(x-3\sqrt{x}+\sqrt{xy}-3y\)

\(=\left(x-3\sqrt{x}\right)+\left(\sqrt{xy}-3y\right)\)

\(=\sqrt{x}\left(\sqrt{x}-3\right)+y\left(\sqrt{x}-3\right)\)

\(=\left(\sqrt{x}-3\right)\left(\sqrt{x}+y\right)\)

 ✰ ღ๖ۣۜDαɾƙ ๖ۣۜBαηɠ ๖ۣۜSĭℓεηтღ✰Giỏi thiệt \(\sqrt{xy}=y\sqrt{x}\)

Đọc lại sách lớp 9, bài LIÊN HỆ GIỮA PHÉP NHÂN VÀ PHÉP KHAI PHƯƠNG

a) \(x^2-xy+x-y\)

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

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

b) \(x^2+5x+6\)

\(=x^2+2x+3x+6\)

\(=x\left(x+2\right)+3\left(x+2\right)\)

\(=\left(x+3\right)\left(x+2\right)\)

\(2xy-x^2-y^2+16\)

\(=16-\left(x-y\right)^2\)

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

x²+3x+3y+xy

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

=(x+3)(x+y)

     x² + 3x + 3y + xy

=   ( x² + xy) + ( 3x + 3y)

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

= ( x + y) ( x + 3) 

=(x+y)(x+3)