la numarator ( x patrat-10xz+25 zpatrat)-y patrat=(x-5z)la patrat-y patrat=(x-5z-y)(x-5z+y)=-(x-5z-y)(-x+5z-y)
la numitor este formula( a+b+c) la patrat=(-x-y+5z)la patrat
-(x-5z-y)(-x-y+5z)/(-x-y+5z) la patrat=(-x+5z+y)/(-x-y+5z). -x-y+5z diferit de 0