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

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

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

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

\(16ty^2+6xt-9t-tx^2\)

\(=t.\left(16y^2+6x-9-x^2\right)\)

\(=t.\left[\left(4y\right)^2-\left(x^2-2.x.3+3^2\right)\right]\)

\(=t.\left[\left(4y\right)^2-\left(x-3\right)^2\right]\)

\(=t.\left(4y-x+3\right)\left(4y+x-3\right)\)

\(x^2-9xy+20y^2\)

\(=\left(x^2-4xy\right)-\left(5xy-20y^2\right)\)

\(=x.\left(x-4y\right)-5y\left(x-4y\right)\)

\(=\left(x-4y\right)\left(x-5y\right)\)

\(x^2+xy-20y^2\)

\(=x^2+2.x.\frac{1}{2}y+\frac{1}{4}y^2-20y^2-\frac{1}{4}y^2\) 

\(=\left(x+\frac{1}{2}y\right)^2-\frac{79}{4}\)

\(=\left(x+\frac{1}{2}y-\frac{\sqrt{79}}{2}\right)\left(x+\frac{1}{2}y+\frac{\sqrt{79}}{2}\right)\)

\(5y^3-10xy^2+5yx^2-20y=5y\left(y^2-2xy+x^2-4\right)\)

                                                              \(=5y\left[\left(x+y\right)^2-4\right]\)

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

Chúc bạn học tốt.

x²-9xy+20y²=x²-4xy-5xy+20y²

nhóm 2 cái đầu, 2 cái cuối.

bạn hoàng tính như nào mà ra đc dòng cuối vậy?

\(x^2+4y^2+4xy-10x-20y+25\)

\(=\left(x^2-10x+25\right)+\left(4xy-20y\right)+4y^2\)

\(=\left(x-5\right)^2+4y\left(x-5\right)+4y^2\)

\(=\left(x-5\right)\left(x-5+4y\right)+4y^2\)

5x – 20y = 5x – 5.4y = 5(x – 4y)

a)4x^2 + y^2 - 4xy - 9t^2 = (2x)^2 - 4xy + y^2 - 9t^2

= (2x - y)^2 - (3t )^2

= ( 2x -y -3t ) ( 2x - y+ 3t)

245555675553556i654e4

a) x² - xy - 20y²

= x² + 4xy - 5xy - 20y²

= x( x + 4y ) - 5y( x + 4y )

= ( x + 4y )( x - 5y )

b) x³ - x²y - 3xy² + 2y³

= x³ + x²y - 2x²y - xy² - 2xy² + 2y³

= ( x³ + x²y - xy² ) - ( 2x²y + 2xy² - 2y³ )

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

= ( x² + xy - y² )( x - 2y )

5x -20y = 5(x-4y)

=5(x-4y)

=5(x-4y)