Math Is Fun Forum

Morgana

Member

Registered: 2009-01-09

Posts: 1

Help!!

Hi, I am new and need help with a problem that a friend has set me, and I have no idea where to start with this.

The problem is

Prove n(Sum)1 x^3 = [n(Sum)1 x] ^2

if there is anyone here who can talk me through this or show me how its solved, id be very grateful to them.

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Help!!

One way you can do it is by mathematical induction. Do you know what mathematical induction is?

Last edited by JaneFairfax (2009-01-09 11:49:09)

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Help!!

Oh, come now.
You've clearly understood Morgana's question despite that speech, I would interpret it the same way you have and I can't think of any other sensible interpretation that this question could have.

Induction is probably the best way to go though.

---

Why did the vector cross the road?
It wanted to be normal.

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Help!!

Another method is to consider

and use the standard formulas for

and

.

Last edited by JaneFairfax (2009-01-09 13:16:39)

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: Help!!

One way you can do it is by mathematical induction. Do you know what mathematical induction is?

I've always found this result rather surprising, and unfortunately induction isn't much of a 'why' method of proving things.