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 :)
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