1.(x+y-z)*(x-y+z) =[x+(y-z)][x-(y-z)]=x²-(y-z)²=x²-y²-z²+2yz2.(x+y+z)*(x-y+z)=[(x+z)+y][(x+z)-y]=(x+z)²-y²=x²+z²+2xz-y²