How to rewrite 2D Gaussian eqn in terms of x?

AI Thread Summary
The discussion focuses on rewriting a 2D Gaussian equation in terms of x, with the initial confusion surrounding the request to express it solely in terms of x and y. Participants clarify that the equation cannot be simplified to only x without specific values for y and f(x,y). A specific example is provided where y is set to 2, allowing for the calculation of x given a constant f(x,y). The equation is presented in a logarithmic form, indicating the steps to isolate x. Overall, the conversation emphasizes the need for specific values to solve for x within the context of the 2D Gaussian function.
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http://upload.wikimedia.org/math/1/9/8/1983171154842b0b061fc42aa5eb7642.png"

How to rewrite this 2D Gaussian eqn in terms of x?
i need to calculate the x and y values.
let x0=0 and y0=0.

is it complex?
 
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What do you mean by "write in terms of x"? It is already written in terms of x and y and cannot be written in terms of x only.

Do you mean "solve for x"? Again, because it is a function of both x and y, you cannot solve it for x alone. You can assume a specific value for y and then solve for x.

But to "solve for x" you would also have to have a specific value of f(x,y).

I simply don't understand what you mean by "calculate the x and y values". In general, x and y can have any real values. What conditions are you placing on f(x,y) to give specific x and y values that you could calculate?
 
yes sorry i mean solve for x

let f(x,y) = y = 2. say
 
I've never seen \sigma so assuming it's to be treated as a constant, yes you certainly can solve for x given y and f(x,y). It's relatively simple too.

-ln\left(\frac{f(x,y)}{A}\right)=\frac{(x-x_0)^2}{2\sigma_x^2}+\frac{(y-y_0)^2}{2\sigma_y^2}

It should be obvious from here how to solve for x.
 
Since ##px^9+q## is the factor, then ##x^9=\frac{-q}{p}## will be one of the roots. Let ##f(x)=27x^{18}+bx^9+70##, then: $$27\left(\frac{-q}{p}\right)^2+b\left(\frac{-q}{p}\right)+70=0$$ $$b=27 \frac{q}{p}+70 \frac{p}{q}$$ $$b=\frac{27q^2+70p^2}{pq}$$ From this expression, it looks like there is no greatest value of ##b## because increasing the value of ##p## and ##q## will also increase the value of ##b##. How to find the greatest value of ##b##? Thanks
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