salut
A(x)= 1-4x²-(1-2x)(2+x)
1)
A(x)= 1-4x²-2-x+4x+2x²
= -2x²+3x-1 => forme 1
2) factorisation de 1-4x² (a-b)(a+b)
=>(1-2x)(1-2x)
A(x)= (1-2x)(1+2x)-(1-2x)(2+x)
= (1-2x)(1+2x-2-x)
= (1-2x)(x-1) => forme 2
3) A(x)=0 => forme 2
1-2x=0 => x=1/2
x-1=0 => x=1 S={ 1/2 ; 1}
A(x)= -1 => forme 1
=> -2x²+3x-1=-1
=> -2x²+3x=0
=> x(-2x+3)=0 x=0 ou x= 3/2 S={ 0 ; 3/2}
A(x)=3x-1 => forme 1
-2x²+3x-1=3x-1
-2x²+3x-1-3x+1=0
-2x²=0 => x=0
4) A(0)= forme 1 => -2*0²+3*0-1=-1
A(racine(3))= forme1
=>-2*(racine(3))²+3*racine(3)-1
=>3*(racine(3))-7
