... k (G( g(x), g( y), g( y)) + G( g(y), g( x), g( x))) G( g(x), g( y), g( y)) + G( g(y), g( x), g( x)) 2k (G( g(x), g( y), g( y)) + G( g(y), g( x )g( x))) ẻứ 2k < 1á ỉ G( g(x), g( y), g( y)) + G( g(y), g( x), g( x)) < G( g(x), ... áỉ G( x, g( x), g( x)) k (G( x, g( x), g( x)) + G( y, g( y), g( y))) è ề ỉ áỉ ỷệ G( y, g( y), g( y)) k (G( x, g( x), g( x)) + G( y, g( y), g( y))) ể G( x, g( x), g( x)) + G( y, g( y), g( y)) 2k (G( x, g( x), g( x)) + G( y, ... G( g(xn) ,g( xn+1), g( xn+1)) k (G( g(xn1), g( xn), g( xn)) + G( g(yn1), g( yn), g( yn))) 2k 2 (G( g(xn2), g( xn1), g( xn1)) + G( g(yn2), g( yn1), g( yn1))) ããããããããã (2k)n (G( g(x0), g( x1), g( x1)) + G( g(y0), g( y1), g( y1)))...