4. (10%) Let f(x) = (x - 1)/(x + 1). Use the definition of the derivative of a function to find the instantaneous rate of change of f(x) at x = -1/2.

II、計算問答題(每大題 10 分，共 20 分。) 1. Mary has T = 40 observations on variables y, $x_1$, and $x_2$. She estimates the following equations by least squares: Residual sum of squares (SSR)=140, $R^2 = 0.8$ where the numbers in parentheses are standard errors. What is the true value of SST in equation (1)? What is the value of $s^2$ (estimated error variance.)?

4. (10%) Let $f(x) = \frac{x - 1}{x + 1}$. Use the definition of the derivative of a function to find the instantaneous rate of change of f(x) at x = -1/2.

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