Question 190055
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*[tex \LARGE \ \ \ \ \ \ \ \ \ \  \frac{1}{F} = \frac{1}{D_i} + \frac{1}{D_o}]


for *[tex \LARGE  D_o = 18] and *[tex \LARGE  D_i = 9]


Just substitute the values and do the arithmetic:



*[tex \LARGE \ \ \ \ \ \ \ \ \ \  \frac{1}{F} = \frac{1}{9} + \frac{1}{18}]


John
*[tex \LARGE e^{i\pi} + 1 = 0]
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