Re: [Phys-L] Conceptual Physics Course

[Brian Blais <bblais@bryant.edu>]

On May 17, 2012, at 11:22 AM, Jeffrey Schnick wrote:

> On a related note, what do you do to convince a person in  a lasting
> manner that the reciprocal of (1/x + 1/y) is not, in general, x+y?

x=y=0

x=y=one million

these two specific examples show that they aren't even close, and can be done with just a little inspection. I try to get my students to ask a few questions to themselves about any term in an expression or an answer to a problem that they are dealing with:  is the answer greater or less than zero?  is the answer small or large compared to 1?

this allows them to catch many of the silly arithmetic errors that they make, and would easily allow one to check the expressions above.


		bb

-- 
Brian Blais
bblais@bryant.edu
http://web.bryant.edu/~bblais
http://brianblais.wordpress.com/