Exercice 17
[tex]A=3x+5x=8x\\B=7x-9x=-2x\\C=3x^2-8x^2=-5x^2\\D=9+2x : \text{impossible}\\E=4x+x=5x\\F=2x^2-x^2=x^2\\G=-9x+4x+5x=-9x+9x=0\\H=5x^2+4 : \text{impossible}\\I=3x^2+2x:\text{impossible}[/tex]
Exercice 23
[tex]A=2 \times (-4x)=-8x\\B=2x^2-4x^2=-2x^2\\C=3x+4+5x+9=8x+13\\D=(-2x) \times (-3x)=6x^2\\E=-4x \times 2x^2=-8x^3\\F=-4x^2-9x^2=-13x^2[/tex]
