Math Help - Factoring Assingment

1. Factoring Assingment

hi, im doing this factoring assignment, and i cant figure out some of the problems , i'd be extremely glad if someone could help me.

(2m+8)^2 - (4m+5)^2 I have no idea how to start with this one

x^2 - 21x -72

(x-2)^2 -16 Is this one a difference of squares? and how do
i resolve it?

25x^2 +30xy + 9y^2 is this a tough polynomial? because i have no
idea how to resolve it, i got confused, or should i
resolve it using common factoring, only i've tried that and didnt work...

2. Originally Posted by lausalas
hi, im doing this factoring assignment, and i cant figure out some of the problems , i'd be extremely glad if someone could help me.

(2m+8)^2 - (4m+5)^2 I have no idea how to start with this one

(2m+8)*(2m+8)-((4m+5)*(4m+5))
foil these out and then simplify.

x^2 - 21x -72
look for terms that multiply to -72 but add to -21
(x- )(x+ )

(x-2)^2 -16 Is this one a difference of squares? and how do
i resolve it?
if you had (x^2-9) this would also be a difference of squares and it would factor to (x+3)(x-3)=0

25x^2 +30xy + 9y^2 is this a tough polynomial? because i have no
idea how to resolve it, i got confused, or should i
resolve it using common factoring, only i've tried that and didnt work...
Not sure about this one. Is that all you were given?

3. thanks you

but im still not sure how to do this one

(x-2)^2 -16, so then, is not a diference of squres, then what is it?

4. Originally Posted by lausalas
thanks you

but im still not sure how to do this one

(x-2)^2 -16, so then, is not a diference of squres, then what is it?
It is a difference of squares. $[x-2]^2-4^2$. Factor it like normal.

5. Originally Posted by lausalas
thanks you

but im still not sure how to do this one

(x-2)^2 -16, so then, is not a diference of squres, then what is it?
It is a difference of squares. I was just giving you an example to go by.
If your problem was (x^2-16) would you know how to do it?
For example, if the problem was (x^2-49). It would factor to (x-7)(x+7)=0
If you foil those two you get back to (x^2-49), right?
For your problem think of the (x-2)^2 as being simply x^2. Everywhere you would put x just put (x-2). Okay?