887 9.1 Systems of Linear Equations 72. 2 x + 3 y = 18 4 x - 5 y = -8 73. 2 x + 3 y - 2 z = -1 8 x - 12 y + 5 z = 5 6 x + 3 y - 1 z = 1 74. - 5 x + 4 y + 3 z = 2 10 x + 3 y - 6 z = 7 5 x + 2 y - 9 z = 6 75. Concept Check For what value(s) of k will the following system of linear equations have no solution? infinitely many solutions? x - 2y = 3 -2x + 4y = k 76. Concept Check Consider the linear equation in three variables x + y + z = 4. Find a pair of linear equations in three variables that, when considered together with the given equation, form a system having (a) exactly one solution, (b) no solution, and (c) infinitely many solutions. (Modeling) Use a system of equations to solve each problem. See Example 8. 77. Find an equation of the line y = ax + b that passes through the points 1-2, 12 and 1-1, -22. 78. Find an equation of the line y = ax + b that passes through the points 13, -42 and 1-1, 42. 79. Find an equation of the parabola y = ax2 + bx + c that passes through the points 12, 32, 1-1, 02, and 1-2, 22. 80. Find an equation of the parabola y = ax2 + bx + c that passes through the points 1-2, 42, 12, 22, and 14, 92. 0 x y (2, 5) (–1, –4) x y (2, 9) (–2, 1) (–3, 4) 0 81. Connecting Graphs with Equations Use a system to find an equation of the line through the given points. 82. Connecting Graphs with Equations Use a system to find an equation of the parabola through the given points. 83. Connecting Graphs with Equations Find an equation of the parabola. Three views of the same curve are given. −10 −10 10 10 −10 −10 10 10 −10 −10 10 10
RkJQdWJsaXNoZXIy NjM5ODQ=