Use the "difference of squares" rule to factor the following expression:
64z^4 -81a^4

So far I have:
(8z^2 +9a^2)(8z^2-9a^2)

Question

Use the "difference of squares" rule to factor the following expression:
64z^4 -81a^4

So far I have:
(8z^2 +9a^2)(8z^2-9a^2)

anonymous · Answer

What do I do next, do I do FOIL to check it and then thats all?

anonymous · Answer

as far as i can tell thats all you can do.  it looks like that second term should factor, but it doesnt (nicely anyways).

anonymous · Answer

That's a bit sneaky, isn't it?

If you take the question literally you should factor the second bracket even with the "ugly" root 2 (or just leave it as root 8).

I'd be tempted to do it on the theory you couldn't lose marks for  an ugly answer but might lose them if you didn't do it.

anonymous · Answer

Well do you need to know what class I am taking to determine if I should go the Ugly way or not?

anonymous · Answer

I think perhaps only you know whether the question is really  expecting you to do it once or twice.

You could put the ugly part as a "note", perhaps...

anonymous · Answer

Well do you need to know what class I am taking to determine if I should go the Ugly way or not?

anonymous · Answer

The ones in the book does not have any square roots. But what is it so I can write it as a note.

anonymous · Answer

(sqrt(8)z -3a)(sqrt(8)z +3a)

(As well, you could turn the sqrt8 into 2sqrt2 if you wanted to,"normally you would")