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

\(=\dfrac{2}{3}x^3y^3-\dfrac{2}{3}x^2y^3+\dfrac{1}{3}x^2y^2+\dfrac{1}{6}xy^2\)

`(2/3xy^2)(x^2y-xy+x/2+1/4)`

`=2/3x^3y^3-2/3x^2y^3+1/3x^2y^2+1/6`

a,= x. [x^2 +3x -5 ]+3.[x^2 +3x -5 ]

=x^3 +3x^2 -5x +3x^2 +9x -15

=x^3 +6x^2+4x-15

b,=xy .[xy+5] -1 . [xy+5]

  =x^2y^2+5xy-xy-5

=x^2y^2+4xy-5

a) \(3x\left(5x^2-2x-1\right)\)

\(=3x.5x^2-3x.2x+3x.\left(-1\right)\)

\(=15x^3-6x^2-3x\)

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

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

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

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

mấy câu sau vt lại đè

Bài 3: 

a: \(=\left(2x-5\right)\left(4x^2+10x+25\right)\)

( x 2 +2xy -3)(-xy)

= (-xy). ( x 2  +2xy – 3)

= (- xy). x 2  + (- xy).2xy + (- xy).(-3)

= -  x 3 y – 2 x 2 y 2  + 3xy

Bài 2: 

a: =>4x(x+5)=0

=>x=0 hoặc x=-5

b: =>(x+3)(x-3)=0

=>x=-3 hoặc x=3

Làm tính nhân:

a. 3 x(5x2 - 2x -1) = 15x3 - 6x2 - 3x

b. (x2+2xy -3)(-xy) = - x3y – 2x2y2 + 3xy

c. 1/2 x2y ( 2x3 - 2/5 xy2 -1 )= x5y - 1/5 x3y3 - 1/2 x2y

a,3x(5x^2-2x-1)

=15x^3-6x^2-3x

a) \(3x\left(5x^2-2x-1\right)\)

\(=15x^3-6x^2-3x\)

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

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

c) \(\dfrac{1}{2}x^2y\left(2x^3-\dfrac{2}{5}xy^2-1\right)\)

\(=x^5y-\dfrac{1}{5}x^3y^3-\dfrac{1}{2}x^2y\)

a) 3x(5x²-2x-1) = 15x³ - 6x² - 3x

b) (x²+2xy-3)(-xy) = -x³y - 2x²y² + 3xy

c) \(\dfrac{1}{2}\)x²y\((\)2x³ - \(\dfrac{2}{5}\)xy² - 1) = x⁵y - \(\dfrac{1}{5}\)x³y³ - \(\dfrac{1}{2}\)x²y