# A little math help?

Discussion in 'Community Discussion' started by P-Worm, Nov 27, 2006.

1. ### P-Worm macrumors 68020

Joined:
Jul 16, 2002
Location:
Salt Lake City, UT
#1
I am reviewing for a test and came across something that I have never seen before and I was hoping someone could clue me in on what is being talked about.

I'm supposed to find the general solution of the following equation:

The standard way to do this is to make the derivatives the exponent of r values and then find the roots and plug them into a prefabricated equation. This is their equation for the roots:

I don't get where this came from. What does y^iv mean anyway? Obviously it has something to do with imaginary numbers.

Thanks for any help you can provide.

P-Worm

2. ### P-Worm thread starter macrumors 68020

Joined:
Jul 16, 2002
Location:
Salt Lake City, UT
#2
Ha, this always seems to happen when I ask for help. I figure it out right after I ask. Just in case you were wondering, the iv is roman numerals for 4 and that means that it is the fourth derivative of y.

Blah.

P-Worm

3. ### psychofreak Retired

Joined:
May 16, 2006
Location:
London
#3
You can't post .tiff images, they don't show. People: if you quote, then copy+paste the link.

4. ### P-Worm thread starter macrumors 68020

Joined:
Jul 16, 2002
Location:
Salt Lake City, UT
#4
It shows fine for me.

P-Worm

5. ### Dandaman macrumors 6502

Joined:
Jan 31, 2004
Location:
soCal
#5
just out of curiousity, why do they put it in roman numerals and not the two? I remember doing stuff like this in my DiffEq class in college a few years ago, but I don't recall why.

daniel

6. ### n-abounds macrumors 6502a

Joined:
Mar 6, 2006
#6
I'd figure y^iv to mean the fourth derivative of y, just like you said. Although, I don't know what y is so I don't know how they get imaginary numbers...

7. ### Eraserhead macrumors G4

Joined:
Nov 3, 2005
Location:
UK
#7
I'd love to help if I could see the images . EDIT: Firefox/Camino won't display them, but Safari will.

Imaginary numbers could work I suppose, you can differentiate them anyway.

EDIT 2: I don't think iv necessarily has to be to do with imaginary numbers, 1 has the square roots of 1, -1, but has fourth roots of 1,-1,i,-i (i^2=-1 and -1^2=1)