Find the number of GPs having $5, 9, 11$ as its three terms

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Find the number of GPs having $5, 9, 11$ as its three terms

The three terms may or may not be consecutive.

I expressed therms as $5,5r^m, 5r^n$ $$r^{n-m}=\frac{11}{9}$$

How should I proceed?

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$$\left(\frac95\right)^n=\left(\frac{11}5\right)^m\\ 3^{2n}5^{m-n}=11^m\text{ or }3^{2n}=11^m5^{n-m}$$ So 11 is a factor of the right-hand side, but not the left.
Contradiction.