Exercise 2.15. Eva Lu Ator, another user, has also noticed the different intervals computed by different but algebraically equivalent expressions. She says that a formula to compute with intervals using Alyssa’s system will produce tighter error bounds if it can be written in such a form that no variable that represents an uncertain number is repeated. Thus, she says, par2 is a ‘‘better’’ program for parallel resistances than par1. Is she right? Why?
不确定的数字一旦出现，无论是加减乘除，无论是在分子还是分母，这个数字的误差都会对最终误差产生积累的效果。所以这种说法是对的。