1) (x+3)(x-5)+2(x+3)(x+6)=0 <=> 1) (x+3)(x-5+2x+12)=0 <=> (x+3)(3x+7)=0
soit x+3 = 0 <=> x1=-3
soit 3x+7 = 0 <=> 3x=-7 <=> x2 = -7/3
2) (x-5)(x+15)=(x-5)(x+7) <=> 2) (x-5)(x+15)-(x-5)(x+7)=0
<=> 2) (x-5)(x+15-x-7)=0 <=> 8(x-5)=0 <=> x-5 = 0 <=> x = 5
3) V5x + 13 = V3x + 6 <=> (V5-V3)x = 6-13 = -7 <=> x= -7/(V5-V3)
4) V2x + V3 > 4x - 5V3 <=> (V2 - 4)x > - 6V3 <=> x > - (6V3)/(V2 - 4)
