Sagot :

A(x)=(16x-49)²-(4x-25)²
      =(16x-49-4x+25)(4x-49+4x-25)
      =(12x-24)(8x-74)

B(x)=x²-2x+1+(3x+4)(x-1)
      =(x-1)²+(3x+4)(x-1)
      =(x-1)(x-1+3x+4)
      =(x-1)(4x+3)

C(x)=(19x-17)²+(11-2x)(17-19x)
      =(19x-17)(19x-17-11+2x)
      =(19x-17)(21x-28)