(a+b)的二次方=1;又(a+b)2=a2+2*a*b+b2=2+2*a*b=1;则2*a*b=-1; a*b=-1/2;又a+b=1; 则a、b为方程x2-x-1/2=0的根;a=-1/2;b=1;所求得结果为1-1/128=127/128