令0.23+0.34+0.56=a
则1+0.23+0.34=1+a-0.56
0.23+0.34+0.56=a
1+0.23+0.34+0.56=1+a
0.23+0.34=a-0.56
所以原式=a(1+a-0.56)-(1+a)(a-0.56)
=a*1+a(a-0.56)-1*(a-0.56)-a(a-0.56)
=a-(a-0.56)
=a-a+0.56
=0.56