la prima: x2(x+3)-16(x+3)= (x+3)(x2-16)= (x+3)(x-4)(x+4)
la a doua: (2x)2-3*3-(2x-3)=(2x-3)(2x+3)-(2x-3)=(2x-3)(2x+3-1)=(2x-3)(2x+2)=(2x-3)2(x+1)
la a treia: (2x)2-(3*radical din x+1)2=(2x-3*radical din x+1)(2x+3*radical din x+1)
la a patra: 9x(x+1)-(x+1)=(x+1)(9x-1)