Bài 1: 

a, (\(x\) - 4).(\(x\) + 4) - (5 - \(x\)).(\(x\) + 1)

= \(x^2\) -  16 - 5\(x\) - 5 + \(x^2\) + \(x\) 

= (\(x^2\) + \(x^2\)) - (5\(x\) - \(x\)) - (16 + 5)

= 2\(x^2\) - 4\(x\) - 21

b, (3\(x^2\) - 2\(xy\) + 4) + (5\(xy\) - 6\(x^2\) - 7)

=  3\(x^2\) - 2\(xy\) + 4 + 5\(xy\) - 6\(x^2\) - 7

= (3\(x^2\) - 6\(x^2\)) + (5\(xy\) - 2\(xy\)) - (7 - 4)

= - 3\(x^2\) + 3\(xy\) - 3

Bài 2:

a, 3\(x^2\).(2\(x\) + y) - 2y(4\(x^2\) - y)

= 6\(x^3\) + 3\(x^2\).y - 8y\(x^2\) + 2y²

= 6\(x^3\) - (8\(x^2\)y - 3\(x^2\)y) + 2y²

= 6\(x^3\) - 5\(x^2\)y + 2y²

a: \(\left(3x+2\right)\left(9x^2-6x+4\right)\)

\(=27x^3+8\)

b: \(\left(x-2y\right)^3-\left(x^2-2xy+y^2\right)\)

\(=x^3-6x^2y+12xy^2-8y^3-x^2+2xy-y^2\)

Bài làm 

\(\frac{4x^3y^2-6x^2y^3}{2xy+2xy\left(y-x\right)}=\frac{2x^2y^2\left(2x-3y\right)}{2xy\left(1+y-x\right)}=\frac{xy\left(2x-3y\right)}{1+y-x}\)

Học tốt 

\(\frac{4x^3y^2-6x^2y^3}{2xy+2xy\left(y-x\right)}=\frac{2x^2y^2\left(2x-3y\right)}{2xy\left(1+y-x\right)}=\frac{xy\left(2x-3y\right)}{y-x+1}\)

A=xy² +4x²y+x³

=> Bậc của đa thức A là:3

\(A=2xy^2+3x^2y-x^3+x^2y-xy^2+2x^3\)

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

    \(=xy^2+4x^2y+x^3\)

\(\Rightarrow\)Bậc của đa thức là \(3\)

A=\(2XY^2+3x^2y-x^3+x^2y-xy^2+2x^3\)

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

\(A=xy^2+4x^2y+x^3\)

b;BẬC LÀ 3

a: =xy(1/3+4-2)=7/3xy

b: =xy^2(-1+3/2+4/3)=(1/3+3/2)xy^2=11/6xy^2

c: =4x^2y^2+2/3x^2y^2-4/3x^2y=-4/3x^2y+14/3x^2y^2

d: =3x^2y^2z+4x^2y^2z-8x^2y^2z=-x^2y^2z

B) Ta có: 2x-2y-x²+2xy-y²

⇔ 2(x-y)-(x²-2xy+y²)

⇔ 2(x-y)-(x-y)²

⇔ (x-y)(2-x+y)

Đúng thì tick nhé

Bài 2: 

\(\Leftrightarrow\left(x-1\right)\left(3x+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-\dfrac{1}{3}\end{matrix}\right.\)

⇔⎡⎣x=1x=−13

1. \(\dfrac{x^3-4x^2+4x}{x^2-4}=\dfrac{x\left(x^2-4x+4\right)}{\left(x+2\right)\left(x-2\right)}=\dfrac{x\left(x-2\right)^2}{\left(x+2\right)\left(x-2\right)}=\dfrac{x\left(x-2\right)}{x+2}\)

Đợi anh chút

\(\dfrac{x^2y+2xy^2+y^3}{2x^2+xy-y^2}=\dfrac{y\left(x^2+2xy+y^2\right)}{2x^2+2xy-xy-y^2}=\dfrac{y\left(x+y\right)^2}{2x\left(x+y\right)-y\left(x+y\right)}\)

\(=\dfrac{y\left(x+y\right)^2}{\left(2x-y\right)\left(x+y\right)}=\dfrac{y\left(x+y\right)}{2x-y}\)