F(x,y,z)=(x+ y').z
F(x,y,z)=x.z+ y'.z
F(x,y,z)=x.z(y+y')+ y'.z(x+x')
F(x,y,z)=x.z.y+x.z.y'+ y'.z.x+y'.z.x'
F(x,y,z)=x.y.z+x.y'.z+ x.y'.z+x'.y'.z