A PDF formed from a multivariate function

Saracen Rue
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Homework Statement


A probability density function, ##p\left(x\right)=\int _{-a}^a\left(f\left(x,\left(a-y\right)\right)-f\left(y,ax\right)\right)dy##, can be formed from the bivariate function ##f\left(x,y\right)=y\sqrt{\left(x-2\right)^2-y}## over the domain ##[0,b]## - where ##b## is the coordinate of the x-intercept.

(a) Determine the values of ##a## and ##b## correct to 5 decimal places
(b) Calculate the expected value, variance and standard deviation of ##p(x)## correct to 4 decimal places
(c) Find the percentage probability of the continuous random variable ##X## being withing ##|a|## standard deviations either side of the mean​

Homework Equations


Knowledge or probability density functions, including integral applications.

The Attempt at a Solution


Well I know that I need to substitute the actual values for ##f\left(x,\left(a-y\right)\right)## and ##f\left(y,ax\right)## into ##p(x)## to be able to integrate ##\int _{-a}^a\left(f\left(x,\left(a-y\right)\right)-f\left(y,ax\right)\right)dy##, and then I'd need to solve ##int_0^b p(x)dx for b and then use that to solve for a. However, when I attempt to do this on my calculator I receive and error message. Does anyone know how I could do this?
 
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Which error message do you get?
 
mfb said:
Which error message do you get?

I receive the message: "ERROR: Insufficient Memory"
 
Maybe you can simplify the function a bit, or use a better calculator.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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