If I have an equation like this

$[2f+(p+q) ]*[2f-(p+q) ]=4pq$

Are any of the three methods below any better than the other?

Are any of them incorrect?
Is there a 'correct' way that should always be used?

Many thanks

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Method 1.

$[2f+(p+q) ]*[2f-(p+q) ]=4pq$

$let\ \ \ 4pq=rs$

$2f+(p+q)=r$

$2f-(p+q)=s$

$4f=r+s\ \ \ \ \ \ \ \ \ \ f=\dfrac{r+s}{4}$

$2(p+q)=r-s\ \ \ \ \ \ \ \ p+q=\dfrac{r-s}{2}$

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Method 2.

$[2f+(p+q) ]*[2f-(p+q) ]=4pq$

$let\ \ \ 4pq=4rs$

$2f+(p+q)=2r$

$2f-(p+q)=2s$

$4f=2r+2s\ \ \ \ \ \ \ \ \ \ \ f=\dfrac{r+s}{2}$

$2(p+q)=2r-2s\ \ \ \ \ \ \ \ p+q=r-s$

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Method 3.

$[2f+(p+q) ]*[2f-(p+q) ]=4pq$

$let\ \ \ 4pq=4rs$

$2f+(p+q)=4r$

$2f-(p+q)=s$

$4f=4r+s\ \ \ \ \ \ \ \ \ \ \ \ \ f=\dfrac{4r+s}{4}$

$2(p+q)=4r-s\ \ \ \ \ \ \ \ p+q=\dfrac{4r-s}{2}$