Different answers for the two ways of computing formulas for parallel resistors
Demonstrate that Lem is right. Investigate the behavior of the system on a variety of arithmetic expressions. Make some intervals 
A
 and 
B
, and use them in computing the expressions 
A/A
 and 
A/B
. You will get the most insight by using intervals whose width is a small percentage of the center value. Examine the results of the computation in center-percent form (see exercise 
2.12
).