SEARCH HOME
Math CentralQuandaries & Queries

search

Question from Adil:

expand the following:
(5x-9)(5x+9)

Hi,

This is an exercise with the distributive law which says that for any numbers $a, b$ and $c$, $a(b + c) = ab + ac.$

I an going to illustrate with a different question,

expand $(3x - 5)(2x + 3).$

To use the distributive law I will take $a = 3x - 5, b = 2x \mbox{ and }c = 3.$ with this I get

\[(3 x - 5)(2x + 3) = (3x - 5) \times 2x + (3x - 5) \times 3 = 6x^2 -10 x + 9x - 15 = 6x^2 -x - 15.\]

Try this with your problem. It simplifies to something simpler than mine.

Penny

About Math Central
* Registered trade mark of Imperial Oil Limited. Used under license.
 

 


Math Central is supported by the University of Regina and the Imperial Oil Foundation.
Quandaries & Queries page Home page University of Regina Imperial Oil Foundation