Factor. s^2(t - u) - 9t^2 (t - u)

Question

dont get this one

Answer 1

Duplicate of http://www.wyzant.com/resources/answers/24891/factor_s_2_t_u_9t_2_t_u, which I answered.

Answer 2

Corry,

 

the common factor for both are (t-u), we can take it out:

 

(t-u)(s^2-9t^2)

 

And because a^2-b^2=(a+b)(a-b), in this case,

 

 s^2-9t^2

=s^2-(3t)^2   [note: s=a, 3t=b in the above formula]

=(s+3t)(s-3t)

 

So the complete factor for this one is (t-u)(s+3t)(s-3t)

 

Hope it helps.

 

Heng