Posted by **Kayleigh** on Sunday, January 4, 2009 at 4:46pm.

i'm having troubles with some sums

how would you factorize completely

9a(squared) - b(squared)?

or an expression like

27x(squared) - 1/3y(squared)

its difficult. have many more.

- Math- Algebra -
**jess**, Sunday, January 4, 2009 at 4:56pm
9a^2 - b^2

= (3a)^2- (b)^2

= (3a+b)(3a-b)

i couldn't understand the second one though. Hope it helps!!! :-)

- Math- Algebra -
**Damon**, Sunday, January 4, 2009 at 4:56pm
whenever you have the difference of two squares

the factors are the sum and the difference of the two that are squared.

a^2-b^2 ( a + b )( a - b )

- Math- Algebra -
**Damon**, Sunday, January 4, 2009 at 5:00pm
27x(squared) - 1/3y(squared)

first take (1/3) out

(1/3) (3^4 x^2 - y^2)

(1/3)(3^2 + y)(3^2 - y)

(1/3)(9+y)(9-y)

- forgot x -
**Damon**, Sunday, January 4, 2009 at 5:02pm
1/3) (3^4 x^2 - y^2)

(1/3)(3^2 x + y)(3^2 - y)

(1/3)(9x+y)(9x-y)

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