Hi,

Most of your problems can be solved using the following 3 identities:
1) 
2) 
3) 

I'm solving a few below - go through these and try the rest yourself.

1) 
=      => Now it is of the form a^3 + b^3

=   --> Using identity (2)

Choice D

2) 

=  => Now it is of the form a^3 - b^3
=   ---> Using identity (1)

Choice E

3) 

=  => Now it is of the form a^2 - b^2
=     ---> Using identity (3)
Choice B

4)
  ---> take out the common factor of -2
= 
=  => Now it is of the form a^2 - b^2
=     ---> Using identity (3)
=    ---> since w^2 - 25 is also of the form a^2 - b^2
Choice E

Hope you get the idea now :)