91Ó°ÊÓ

In Exercises 19 - 44, solve the system of linear equations and check any solution algebraically. \( \left\\{\begin{array}{l}2x + 4y + z = 1\\\x - 2y - 3z = 2\\\x + 4y + z = 0\end{array}\right. \)

In Exercises 21-32, use a graphing utility to graph the inequality. \( y \ge \dfrac{5}{9}x - 2 \)

In Exercises 21 - 34, solve the system by the method of substitution. \( \left\\{\begin{array}{l}1.5x + 0.8y = 2.3\\\0.3x - 0.2y = 0.1\end{array}\right. \)

In Exercises 13 - 30, solve the system by the method of elimination and check any solutions algebraically. \( \left\\{\begin{array}{l}0.2x - 0.5y = -27.8\\\0.3x + 0.4y = 68.7\end{array}\right. \)

In Exercises 19 - 44, solve the system of linear equations and check any solution algebraically. \( \left\\{\begin{array}{l}2x + y - z = 7\\\x - 2y + 2z = -9\\\3x - y + z = 5\end{array}\right. \)

In Exercises 25-28, find the minimum and maximum values of the objective function and where they occur, subject to the constraints \( x \ge 0, y \ge 0, x + 4y \le 20, x + y \le 18 \), and \( 2x + 2y \le 21 \). \( z = x + 5y \)

In Exercises 19-42, write the partial fraction decomposition of the rational expression. Check your result algebraically. \( \dfrac{1}{x^2 - 1} \)

In Exercises 19-42, write the partial fraction decomposition of the rational expression. Check your result algebraically. \( \dfrac{1}{4x^2 - 9} \)

In Exercises 21-32, use a graphing utility to graph the inequality. \( y \le 6 - \dfrac{3}{2}x \)

In Exercises 21 - 34, solve the system by the method of substitution. \( \left\\{\begin{array}{l}0.5x + 3.2y = 9.0\\\0.2x - 1.6y = -3.6\end{array}\right. \)