R = (\frac{1 - n}{1 + n})^{2} = (\frac{- 1}{2, 5})^{2} = 0, 04

${R = \bigg( \frac{1-n}{1+n} \bigg)^2 = \bigg( \frac{-1}{2,5} \bigg)^2 = 0,04}$

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