Question

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

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

\(c)\left(x^2-6\right)\left(x+2\right)+\left(x+3\right)\left(x-x^2\right)\)

\(d)x\left(x-y\right)-y\left(x-y\right)\)

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

\(f)3x\left(12x-4\right)-9x\left(4x-3\right) \)

 

Answer 1

a) ( x² - 5 )( x + 3 ) = x³ + 3x² - 5x - 15

b) ( x + 4 )( x - x² ) = x² - x³ + 4x - 4x² = -x³ - 3x² + 4x 

c) ( x² - 6 )( x + 2 ) + ( x + 3 )( x - x² ) = x³ + 2x² - 6x - 12 + x² - x³ + 3x - 3x² = -3x - 12 = -3( x + 4 )

d) x( x - y ) - y( x - y ) = ( x - y )( x - y ) = ( x - y )²

e) x²( x + y ) - x( x² - y ) = x³ + x²y - x³ + xy = x²y + xy = xy( x + 1 ) 

f) 3x( 12x - 4 ) - 9x( 4x - 3 ) = 36x² - 12x - 36x² + 27x = 15x 

Answer 2

Bài làm

a) ( x² - 5 )( x + 3 ) 

= x³ + 3x² - 5x - 15

b) ( x + 4 )( x - x² )

= ( x + 4 ) . x( 1 - x )

= x( x + 4 )( 1 - x )

= x( x - x² + 4 - 4x )

= x( 4 - x² - 3x )

= 4x - x³ - 3x² 

c) ( x² - 6 )( x + 2 ) + ( x + 3 )( x - x² )

= ( x - 3 )( x + 3 )( x + 2 ) + ( x + 3 )( x - x² )

= ( x + 3 )[ ( x - 3 )( x + 2 ) + ( x - x² )]

= ( x + 3 ) [ x² + 2x - 3x - 6 + x² - x² ]

= ( x + 3 ) ( x² - x - 6 )

= x³ - x² - 6x + 3x² - 3x - 18

= x³ + 2x² - 9x - 18

d) x( x - y ) - y( x - y )

= ( x - y )( x - y )

= ( x - y )² 

= x² - 2xy + y

e) x²( x + y ) - x( x² - y )

= x³ + x²y - x³ + xy

= x²y + xy

f) 3x( 12x - 4 ) - 9x( 4x - 3 )

= 3x . 3( 4x - 1 ) - 9x( 4x - 3 )

= 9x( 4x - 1 ) - 9x( 4x - 3 )

= 9x( 4x - 1 - 4x + 3 )

= 9x . 2

= 18x

Answer 3

Bài làm

~ Mik làm lại câu f) mik bỏ nhầm số ra ngoài ~

3x( 12x - 4 ) - 9x( 4x - 3 )

= 3x[( 12x - 4 ) - 3( 4x - 3 ) ]

= 3x( 12x - 4 - 12x + 9 )

= 3x . 5

= 15x

Answer 4

dề bài là j vậy