Bonjour,
A=
3x*5x = 15x²
3x*2= 6x
-1 * 5x = -5x
-1 * 2 = -2
=> 15x² +6x -5x -2 = 15x² +x -2
B=
12x² -40x +15x +15x -50 + 10x² -20x +4x -8
12x² + 10x² -40x +15x +15x +4x -20x -50 -8
22x² -26x -58
C=
5x² y +7xz
x( 5xy + 7z)
