Bonjour !
[tex]A(x)= 3(x-5)^2+(x-5)(2x+1)\\\\A(x)= (x-5)[3(x-5)+2x+1]\\\\A(x)= (x-5)(3x-15+2x+1)\\\\A(x)= (x-5)(5x-14)\\\\\\B(x)=4x^2-1\\\\B(x)=2^2x^2-1^2\\\\B(x)=(2x)^2-1^2\\\\B(x)=(2x-1)(2x+1)\\\\\\C(x)=(3x-4)^2+5(4-3x)\\\\C(x)=(3x-4)^2+5[-(3x-4)]\\\\C(x)=(3x-4)^2-5(3x-4)\\\\C(x)=(3x-4)(3x-4-5)\\\\C(x)=(3x-4)(3x-9)\\\\C(x)=(3x-4)*3(x-3)\\\\C(x)=3(3x-4)(x-3)\\\\\\D(x)=x^2-2x+1\\\\D(x)=x^2-2x*1+1^2\\\\D(x)=(x-1)^2\\\\\\[/tex]
[tex]E(x)=(2x+3)^2-(5x-1)^2\\\\E(x)=[2x+3-(5x-1)][2x+3+(5x-1)]\\\\E(x)=(2x+3-5x+1)(2x+3+5x-1\\\\E(x)=(-3x+4)(7x+2)[/tex]
Voilà !
