(3+5/7-2/3)×(1/5+1/7+1/13)-(1/5-1/7+1/13)×3+(1/5+1/7+1/13)×(2/3-7/5)=(1/5+1/7+1/13)×(3+5/7-2/3+2/3-7/5)-(1/5-1/7+1/13)×3=(1/5+1/7+1/13)×(3+5/7-7/5)-(1/5-1/7+1/13)×3-------------------------如果...