• Oct 21st 2008, 12:24 AM
cupcake
Hi,

I'm having trouble solving this equation.. I know it is supposed to turn out a quadratic equation, but I just can't do the math.. Would be incredibly grateful if anyone could help!! (Itwasntme)

Here it goes:

0,6 = √(Wa*0,4390)^2 + (Wb*0,8235)^2 + 2*(Wa*0,4390)*(Wb*0,8235)*0,253454

Now the squareroot is supposed to cover the entire right side of the equation. Wa and Wb are unknowns.
• Oct 21st 2008, 12:36 AM
U-God
Are you looking to solve for them numerically or in terms of each other? As far as I know if you only have one equation and yet two unkowns you cannot solve for them numerically. Someone could correct me though.
• Oct 21st 2008, 12:41 AM
cupcake
Anyway, numerically.. Sorry, I forgot to replace Wb with 1-Wa.. What I'm trying to do here is find unknown weights in a portfolio of two assets. Since Wa + Wb = 1, Wb = 1-Wa.
For simplicity, I replaced Wa with X.

Here is the new equation:

0,6 = √(X*0,4390)^2+((1-X)*0,8235)^2+2*(X*0,4390)*((1-X)*0,8235)*0,253454
• Oct 21st 2008, 12:50 AM
U-God
Oh ok, I'd square both sides, expand all of your brackets, collect like terms. Bring all terms to one side, so the other side is zero and then apply the quadratic formula.
• Oct 23rd 2008, 10:26 PM
CaptainBlack
Quote:

Originally Posted by cupcake
Anyway, numerically.. Sorry, I forgot to replace Wb with 1-Wa.. What I'm trying to do here is find unknown weights in a portfolio of two assets. Since Wa + Wb = 1, Wb = 1-Wa.
For simplicity, I replaced Wa with X.

Here is the new equation:

0,6 = √(X*0,4390)^2+((1-X)*0,8235)^2+2*(X*0,4390)*((1-X)*0,8235)*0,253454

Try replacing:

√(X*0,4390)^2

by

X*0,4390

and then simplifying

CB
• Oct 23rd 2008, 10:29 PM
U-God
Quote:

Originally Posted by CaptainBlack
Try replacing:

√(X*0,4390)^2

by

X*0,4390

and then simplifying

CB

But I think he said in his original post that the square root covers the entire RHS