Let $x$ and $y$ be real numbers such that \[xy - \frac{x}{y^2} - \frac{y}{x^2} = 3.\]Find the sum of all possible values of $(x - 1)(y - 1).$

Name the most appropriate metric unit for each measurement like the mass of cow

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The first-serve percentage of a tennis player in a match is normally distributed with a standard deviation of 4.3%. if a sample of 15 random matches of the player is taken, the mean first-serve percentage is found to be 26.4%. what is the margin of error of the sample mean? a. 0.086% b. 0.533% c. 1.11% d. 2.22%