Bonjour,
(3x+1)(2-3x)-(5x-1)(3x+1)=0 <=> (3x+1)(2-3x-(5x-1))=0
<=> (3x+1)(2-3x-5x+1)=0
<=> (3x+1)(3-8x)=0
<=> 3x+1=0 ou 3-8x=0
<=> 3x=-1 ou 8x=3
<=> x=-1/3 ou x=3/8
(2x+4)(3-x)=(x+2)(5x-7) <=> (2x+4)(3-x)-(x+2)(5x-7)=0
<=> 2(x+2)(3-x)-(x+2)(5x-7)=0
<=> (x+2)(2(3-x)-(5x-7))=0
<=> (x+2)(6-2x-5x+7)=0
<=> (x+2)(13-7x)=0
<=> x+2=0 ou 13-7x=0
<=> x=-2 ou 7x=13
<=> x=-2 ou x=13/7
(2x+3)(6x+7)+(2-4x)(3x+1)=3x-7 <=> (2x+3)(6x+7)+(2-4x)(3x+1)-(3x-7)=0
<=> 12x²+18x+14x+21+6x+2-12x²-4x-3x+7=0
<=> 31x+30=0
<=> 31x=-30
<=> x=-30/31
