Sagot :

Bonjour,

A=(5-x)(8x-6)

= 40x -30 -8x² +6x

= -8x² +46x -30

B=(2x+3)(5x-9)

= 10x² -18x +15x -27

= 10x² -3x -27

C=(4+x)(2-x)+(x+3)(2x+4)

= 8 -4x +2x -x² + 2x² +4x +6x +12

= x² +8x +20