\(a,-2xy^2\left(x^3y-2x^2y^2+5xy^3\right)\\ =-2x^4y^3+4x^3y^4-10x^2y^5\\ b,\left(-2x\right)\left(x^3-3x^2-x+1\right)\\ =-2x^4+6x^3+2x^2-2x\\ c,\left(-10x^3+\dfrac{2}{5}y-\dfrac{1}{3}z\right)\left(-\dfrac{1}{2}zy\right)\\ =5x^3yz-\dfrac{1}{5}y^2z+\dfrac{1}{6}yz^2\\ d,3x^2\left(2x^3-x+5\right)=6x^5-3x^3+15x^2\\ e,\left(4xy+3y-5x\right)x^2y=4x^3y^2+3x^2y^2-5x^3y\\ f,\left(3x^2y-6xy+9x\right)\left(-\dfrac{4}{3}xy\right)\\ =-4x^3y^2+8x^2y^2-12x^2y\)

`Answer:`

\(a)\left(-3x^2y-2xy^2+6\right)+\left(-x^2y+5xy^2-1\right)\)

\(=-3x^2y-2xy^2+6+-x^2y+5xy^2-1\)

\(=\left(-3x^2y-x^2y\right)+\left(-2xy^2+5xy^2\right)+\left(6-1\right)\)

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

\(b)\left(1,6x^3-3,8x^2y\right)+\left(-2,2x^2y-1,6x^3+0,5xy^2\right)\)

\(=1,6x^3-3,8x^2y+-2,2x^2y-1,6x^3+0,5xy^2\)

\(=\left(1,6x^3-1,6x^3\right)+\left(-3,8x^2y+-2,2x^2y\right)+0,5xy^2\)

\(=-6x^2y+0,5xy^2\)

\(c)\left(6,7xy^2-2,7xy+5y^2\right)-\left(1,3xy-3,3xy^2+5y^2\right)\)

\(=6,7xy^2-2,7xy+5y^2-1,3xy+3,3xy^2-5y^2\)

\(=\left(6,7xy^2+3,3xy^2\right)+\left(-2,7xy-1,3xy\right)+\left(5y^2-5y^2\right)\)

\(=10xy^2+-4xy\)

\(=10xy^2-4xy\)

\(d)\left(3x^2-2xy+y^2\right)+\left(x^2-xy+2y^2\right)-\left(4x^2-y^2\right)\)

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

\(=\left(3x^2+x^2-4x^2\right)+\left(-2xy-xy\right)+\left(y^2+2y^2+y^2\right)\)

\(=-3xy+4y^2\)

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

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

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

\(=-1\)

1)

a) => 16x² - 8x + 1 - 8(2x² + 3x - 4x - 6) = 15

=> 16x² - 8x + 1 - 8(2x² - x - 6) = 15

=> 16x² - 8x + 1 - 16x² + 8x + 48 = 15

=> 49 = 15 (?) (vô lí)

=> Không tìm được x thoả mãn

b) (5x - 2)(x - 2) - 4(x - 3) = x² + 3

=> 5x² - 10x - 2x + 4 - 4x + 12 = x² + 3

=> 5x² - 16x + 16 = x² + 3

=> 4x² - 16x + 16 = 3

=> (2x)² - 2.2x.4 + 4² = 3

=> (2x - 4)² = 3

=> \(\left[{}\begin{matrix}2x-4=\sqrt{3}\\2x-4=-\sqrt{3}\end{matrix}\right.\)           \(\Rightarrow\left[{}\begin{matrix}x=\dfrac{4+\sqrt{3}}{2}\\x=\dfrac{4-\sqrt{3}}{2}\end{matrix}\right.\)

Mong bạn xem lại đề bài!

2) 

a) 5x² - 10xy + 5y² - 20z²

= 5(x² - 2xy + y² - 4z²)

= 5[(x - y)² - (2z)²]

= 5(x - y - 2z)(x - y + 2z)

b) a³ - ay - a²x + xy

= a(a² - y) - x(a² - y)

= (a - x)(a² - y)

c) 3x² - 6xy + 3y² - 12z²

= 3(x² - 2xy + y² - 4z²)

= 3[(x - y)² - (2z)²]

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

d) x² - 2xy + tx - 2ty

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

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

Mình tính thẳng ra nhé.

a) -A+B-C= -4x^2 + 2xy - 3y^2 + 3y + 7.

b) A+B-(-C)= -5y^2 = 2xy - 4x + 9y + 5.

a, -x - y² + x² - y = (x² - y²) - (x + y)

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

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

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

= (x - 5)(x + y)
c, x² - 5x + 5y - y² = (x - y)(x + y) - 5(x - y)

= (x - y)(x + y - 5)
d, 5x³ - 5x²y - 10x² + 10xy = 5x²(x - y) - 10x(x - y)

= 5x(x - y)(x - 2)
e, 27x³ - 8y³ = (3x - 2y)(9x² + 6xy + 4y²)
f, x² - y² - x - y = (x - y)(x + y) - (x + y)

= (x + y)(x - y - 1)
g, x² - y² - 2xy + y² = (x² - 2xy + y²) - y²

= (x - y)² - y²

= (x - y - y)(x - y + y) = x(x - 2y)
h, x² - y² + 4 - 4x = (x² - 4x + 4) - y²

= (x - 2)² - y²

= (x - y - 2)(x + y - 2)
i, x³ + 3x² + 3x + 1 - 27z³ = (x + 1)³ - 27z³

= (x+1-3z)(x²+2x+1+3xz+3z+9z²)
k, 4x² + 4x - 9y² + 1 = (2x + 1)² - 9y²

= (2x - 3y + 1)(2x + 3y + 1)
m, x² - 3x + xy - 3y = x(x - 3) + y(x - 3)

= (x - 3)(x + y)

a) x^2+2xy+y^2-16

=(x+y)²-16

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

b) 3x^2+5x-3xy-5y

=(3x²-3xy)+(5x-5y)

=3x(x-y)+5(x-y)

=(x-y)(3x+5)

c) 4x^2-6x^3y-2x^2+8x

ko bik hoặc sai đề

d) x^2-4-2xy+y^2

=(x-y)²-4

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

e) x^3-4x^2-12x+27

=sai đề

g) 3x^2-18x+27

=3(x²-6x+9)

=3(x-3)²

h) x^2-y^2-z^2-2yz

=x²-(y²+z²+2yx)

=x²-(y+z)²

=(x-y-z)(x+y+z)

k) 4x^2(x-6)+9y^2(6-x)

=4x²(x-6)-9y²(x-6)

=(x-6)(4x²-9y²)

=(x-6)(2x-3y)(2x+3y)

l)6xy+5x-5y-3x^2-3y^2

=(5x-5y)+(-3x²+6xy-3y²)

=5(x-y)-3(x²-2xy+y²)

=5(x-y)-3(x-y)²

=(x-y)(5-3(x-y))

=(x-y)(5-3x+3y)