Sagot :

APOUN

A=(3x+1) (x-3)-(x-3)²

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

A=3x*x +3x*(-3) +1*x +1*(-3) - x*x +x*(-3) -3*x -3*(-3)

A=3x²-9x+x-3 - x²-3x-3x+9

A=3x²-x² -9x+x-3x-3x -3+9

A=2x²-14x+6