Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » Inactive » calc_reform

Topic: Re: quadratic formula
Replies: 1   Last Post: May 1, 2001 12:42 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Joan Reinthaler

Posts: 110
Registered: 12/6/04
Re: quadratic formula
Posted: May 1, 2001 12:42 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

As a teacher of high school kids who study the quadratic formula in
algebra classes, I see all sorts of good reasons to spend time with it.
1. Kids ought to be encouraged to generalize their results at every
oportunity. Programmable calculators make this worth their while when
they
can use their generalization to write a quadratic equation-solving program
(I know, there is a dedicated function built in to the TI-83 etc. but it's
much nicer for the kids to write their own first - also, the first time
their discriminent is negative and they get an error message is a
wonderful opportunity for further discussion).
2. The understanding about what it means "to be in the form of", as in, to
use the formula, an equation must be in the form of ax^2 + bx + c = 0 is
more sophisticated than most of us recognize, and it is essential.
3. I encourage kids to approximate rational values for the roots they get
when using the quadratic formula - in their head (i.e. "Root of 21 is
about 4 1/2 so 3 +/- root 21 is approx 7.5 or -1.5 and so forth - all
things that contribute to a secure number sense.
4. Why is the sum of the roots rational (given rational
coefficients)? how about the product? The formula leads to discussions
about conjugate pairs.

It seems to me that the quadratic formula offers a lot of opportunity to
be playful with mathematical ideas and the notion that it can be dispensed
with because calculators do it job better is only true if math is
considered only as a bottom line and not as inquiry.

Joan Reinthaler
Sidwell Friends School



------------------------------------------------------------

-HOW TO UNSUBSCRIBE

To UNSUBSCRIBE from the calc-reform mailing list,
send mail to:

majordomo@ams.org

with the following in the message body:

unsubscribe calc-reform your_email_address


-Information on the subject line is disregarded.





Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.