Sagot :
(5-3x+2y-2x+y)-(3x-7y+9)= (5-5x+3y)-(3x-7y+9)= 5-5x+3y-3x+7y-9= -8x+10y-4= 2(-4x+5y-2)
[tex][5-3x+2y-(2x-y)]-(3x-7y+9)\\\\=(5-3x+2y-2x+y)-3x+7y-9\\\\=(5-5x+3y)-3x+7y-9\\\\=5-5x+3y-3x+7y-9\\\\=-8x+10y-4[/tex]