Multiplying polynomials: (4x - 5)(4x + 5)

G L A M O R O U S x

New member
Joined
May 8, 2007
Messages
1
hey. ummm.. well im new, and i really need help on muiltyplying polynomials. like this one for example::

(4x-5)(4x+5)

i think i might have to use the FOIL method, but i really dont know. HELP!
i really need help, or ill have to go to summer school!

plz and thx,
ali
 
Welcome aboard G L A M O R O U S x!

You could use FOIL, but notice we have a difference of squares.

Whenever you have: (a + b) (a - b) the equations will be in the form a<sup>2</sup> - b<sup>2</sup>

So find a and b:

(a - b) (a + b)
(4x - 5)(4x + 5)

And plug it into: a<sup>2</sup> - b<sup>2</sup>

If that seems to confusing, just use FOIL and you'll see that the middle term with the x cancels.

Oh you don't understand FOIL? Here's a good example, straight from out site: Link
 
G L A M O R O U S x said:
(4x-5)(4x+5)
i really need help, or ill have to go to summer school!
If you can't do that one (quite basic), then it appears
you missed classes: you should go to summer school :shock:
 
As jonboy wrote, your polynomial is of the form (a + b)(a - b).

It just so happens that the difference of a and b multiplied by the sum of a and b is the difference of their squares. (a - b)(a + b) = a^2 - b^2

Learn that identity (called an identity as it is true for all real values of a and b), as you'll be using it in higher and more advanced math courses.
 
Top