16.解:(1)x2-4x+2=0,小多怎后同x2-4x=-2,公x2-4x+4=2,(x2)2=2,x-2=士2,(2)x(x-5)+x5=0,x(x5)+(x-5)=0,(x+1)(x-5)=0,违者必究故1=5,x2=一1.……10分