Teacher2Teacher |
Q&A #740 |
From: Gail
(for Teacher2Teacher Service)
Date: Nov 03, 1998 at 18:37:27
Subject: Re: Activity to show (a+b)^2 = (a+b)(a+b)
I am an elementary teacher, but I wonder if you could use what we use to
demonstrate multiplication. It is similar to algeblocks, which show the
geometric model for agebraic equations. My students set up a multiplication
problem by building a rectangle that has sides the lengths of the two
factors. So, if you were finding 13 x 13, you would use unit blocks to build
a frame for a rectangle that had a ten and three ones vertically, and a ten
and three ones horizontally (this is hard to explain without pictures.
To build the rectangle, you just fill in the frame. The side that has a ten
by ten space would fit a hundred, and the part with a three ones by ten piece
would fit three tens (there are two of them.) The part that is left to fill
is the three ones by three ones part holds 9 ones.
If you built that, and pointed out that the sides were 4 + 9 (hence, 4 + 9
squared and were also 13, then (4 + 9) (4 + 9) = 13 x 13.
-Gail, for the Teacher2Teacher service
[Privacy Policy] [Terms of Use]
Math Forum Home ||
The Math Library ||
Quick Reference ||
Math Forum Search