Developper puis reduire (2x+1)(x-4) (x-3)(2x-3) (x+2)-(2x-1) (2x-3)(3x+5) (x+3)(2-4x) Mercii

Développer puis réduire
(2x+1)(x-4)
= 2x² - 8x + x - 4
= 2x² - 7x - 4

(x-3)(2x-3)
= 2x² - 3x - 6x + 9
= 2x² - 9x + 9

(x+2)-(2x-1)
= x + 2 - 2x + 1
= - x + 3

(2x-3)(3x+5)
= 6x² + 10x - 9x - 15
= 6x² + x - 15

(x+3)(2-4x)
= 2x - 4x² + 6 - 12x
= - 4x² - 10x + 6

= ( 2x + 1 ) ( x - 4 )
= 2x * x + 2x * ( - 4 ) + 1 * x + 1 * ( - 4 )
= 2x² - 8x + x - 4
= 2x² - 7x - 4 

= ( x - 3 ) ( 2x - 3  )
= x * 2x + x * ( - 3 ) - 3 * 2x - 3 * ( - 3 )
= 2x² - 3x - 6x + 9
= 2x² - 9x + 9

= ( x + 2 ) - ( 2x - 1 )
= x + 2 - 2x + 1
= - x + 3

= ( 2x - 3 ) ( 3x + 5 )
= 2x * 3x + 2x * 5 - 3 * 3x - 3 * 5
= 6x² + 10x - 9x - 15
= 6x² + x - 15

= ( x + 3 ) ( 2 - 4x )
= x * 2 + x * ( - 4x ) + 3 * 2 + 3 * ( - 4x )
= 2x - 4x² + 6 - 12x
= - 4x² - 10x + 6