Recent content by rhuelu

how would you prove this?

I would appreciate some help with this problem. Assuming X and Y are independent, I'm trying to find the correlation between XY and Y in terms of the means and standard deviations of X and Y. I'm not sure how to simplify cov(XY,Y)=E(XYY)-E(XY)E(Y) =E(XY^2)-E(X)E(Y)^2. If X and Y are...

I would appreciate some help with this problem. Assuming X and Y are independent, I'm trying to find the correlation between XY and Y in terms of the means and standard deviations of X and Y. I'm not sure how to simplify cov(XY,Y)=E(XYY)-E(XY)E(Y) =E(XY^2)-E(X)E(Y)^2. If X and Y are...

How would I integrate udu/du ?

it doesn't seem like this is the most formal logic in the world...is it trivial that the matrices constructed have ranks of n-1 and 1 or does this need to be shown as well

I'm trying to show that any matrix X with rank n can be written as the sum of matrices Z and Y with rank n-1 and 1, respectively. Since X,Y, Z have the same dimensions, is this a simple matter of saying pick one of the columns in X with a pivot. Let Z= X with this column replaced by zeroes...

How can you prove that matrix X with rank n can be written as the sum of matrices Y and Z where Y has rank n-1 and Z has rank of 1. Thanks!

nevermind, i got it

how would I got about finding the value of the integral from negative infinity to positive infinity if I have 2 different expressions depending on the value of x-a?

oh ok thanks

I'm not really sure how to deal with the absolute value

Exactly. Thanks.

integral of x*(1/2b)*exp(-abs(x-a)/b) sorry about the format, I don't know how to use the signs. this looks like an integration by parts, but I'm not really seeing how to work it out thanks!

here's a tough one... find the values of x for which the matric has no, one, and inf many solutions A= (1 -2 3 1; 2 x 6 6; -1 -3 x-3 0)

thanks...that makes sense. Do you think this logic still holds if we only know that F(x) is right continuous? This is one of the properties of a cdf.