Question

Thực hiện các phép tính sau :

a. (3x - 2) (4x + 5) - 6x (2x - 1)

b. (2x - 5)² - 4(x + 3) (x - 3)

c. (2x³ - 5x² + 7x - 6) : (2x - 3)

Answer 1

a) ( 3x - 2 )( 4x + 5 ) - 6x( 2x - 1 )

= 12x² + 7x - 10 - 12x² + 6x

= 13x - 10

b) ( 2x - 5 )² - 4( x + 3 )( x - 3 )

= 4x² - 20x + 25 - 4( x² - 9 )

= 4x² - 20x + 25 - 4x² + 36

= 61 - 20x

c) 2x³ - 5x² + 7x - 6

= 2x³ - 3x² - 2x² + 3x + 4x - 6

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

= ( 2x - 3 )( x² - x + 2 )

=> ( 2x³ - 5x² + 7x - 6 ) : ( 2x - 3 ) = x² - x + 2

Answer 2

a, (3x - 2 ) (4x + 5) - 6x (2x -1) = ( 7x + 15x -8x - 10 ) - ( 12x² -6x ) = 7x² + 15x - 8x -10 -12x² + 6x = -5x² + x - 10