Répondre :
f(x)=(2x-3)²-(4x+7)²
=4x²-12x+9-16x²-56x-49
=-12x²-68x-40
f(x)=(2x-3)²-(4x+7)²
=(2x-3+4x+7)(2x-3-4x-7)
=(6x+4)(-2x-10)
=-4(3x+2)(x+5)
f(x)=-40
-12x²-68x-40=-40
-12x²-68x=0
x=0 ou x=-17/3
f(0)=-40
f(-5)=0
f(rac(3))=-76-68rac(3)
=4x²-12x+9-16x²-56x-49
=-12x²-68x-40
f(x)=(2x-3)²-(4x+7)²
=(2x-3+4x+7)(2x-3-4x-7)
=(6x+4)(-2x-10)
=-4(3x+2)(x+5)
f(x)=-40
-12x²-68x-40=-40
-12x²-68x=0
x=0 ou x=-17/3
f(0)=-40
f(-5)=0
f(rac(3))=-76-68rac(3)