a) (x+1) ((x+1) la a doua - 4)=
= (x+1) (x+1+2) (x+1-2)
= (x+1) (x+3) (x-1)
b) x la a treia - 15x la a doua+ 75x-125-x-5=
= x la a treia- 15x la a doua -130 +74x
c) (x-1) ((x-1) la a doua-9)=
=(x-1) (x-1-3) (x-1+3)
=(x-1) (x-4) (x+2)
dai factor comun la fiecare
