Réponse :
2-4/1-x
=2(1-x)-4/1-3
=2-2x-4/1-x
=-2-2x/1-x
=-2+2x/1-x
2x+5/3x-1+1
=1(3x-1)+2x+5/3x-1
=3x-1+2x+5/3x-1
=5x+4/3x-1
3*x/2
=3x/2
x+3/x
=x²/x+3/x
=x²+3/x
2x+5/3x-1-3x-2/5x-3
=(2x+5)*(5x-3)-(3x-2)*(3x-1)/(3x-1)*(5x-3) (produit en croix)
=10x²-6x+25x-15-(9x²-3x-6x+2)/15x²-9x-5x+3 (on développe)
=10x²-6x+25x-15-9x²+3x+6x-2/15x²-9x-5x+3
=x²+28x-17/15x²-14x+3
