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# Simple "show that" question! watch

1. Hello there!

I have this really simple looking "show that" question to do but can't seem to verify that LHS = RHS for some reason! Can someone please point out where am I going wrong/guide me on this?

Here are my workings:

Basically, I just substituted the value of z in the LHS of the equation to be proven but couldn't manage to arrive at 0.

Thank you so much!

Merry Christmas, pals!

Sid
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2. (Original post by Sidhant Shivram)
Hello there!

I have this really simple looking "show that" question to do but can't seem to verify that LHS = RHS for some reason! Can someone please point out where am I going wrong/guide me on this?

Here are my workings:

Basically, I just substituted the value of z in the LHS of the equation to be proven but couldn't manage to arrive at 0.

Thank you so much!

Merry Christmas, pals!

Sid

the plan is
correctly expand (that is correct in your workings)
after the cancellations there will be 4 terms
factorize 3(4+√15)1/3(4-√15)1/3 out of the "bigger" two terms
then it wraps up after 2 lines
3. (Original post by TeeEm)

the plan is
correctly expand (that is correct in your workings)
after the cancellations there will be 4 terms
factorize 3(4+√15)1/3(4-√15)1/3 out of the "bigger" two terms
then it wraps up after 2 lines
Ah! I see! Thank you so much! It helped (:
4. (Original post by Sidhant Shivram)
Ah! I see! Thank you so much! It helped (:
my pleasure
5. (Original post by Sidhant Shivram)
..
You can get this to fall out very quickly: Note that , and so if then (*)

Then . You can quickly reduce the last two terms using (*).
6. (Original post by DFranklin)
You can get this to fall out very quickly: Note that , and so if then (*)

Then . You can quickly reduce the last two terms using (*).
Oh yes! Thanks!

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Updated: December 26, 2014
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