Exam 10: Systems and Matrices

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Solve the problem. -Michael's bank contains only nickels, dimes, and quarters. There are 51 coins in all, valued at \$4.15. The number of nickels is 5 short of being three times the sum of the number of dimes and quarters. How many dimes are in the bank?

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Provide an appropriate response. -Suppose that you are solving a system of three linear equations by the Gauss-Jordan method and obtain the following augmented matrix. [1711300000018326]\left[ \begin{array} { r r r | r } 1 & - 7 & 11 & - 30 \\0 & 0 & 0 & 0 \\0 & 18 & - 3 & 26\end{array} \right] What conclusion can you draw about the solutions of the system?

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Solve the equation for x. - 251x=3\left| \begin{array} { r r } - 2 & 5 \\1 & x\end{array} \right| = - 3

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Use the Gauss-Jordan method to solve the system of equations. If the system has infinitely many solutions, give the solution with y arbitrary. - 2x+5y=-7 -6x-15y=21

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Provide an appropriate response. -Suppose that AA and BB are two matrices such that A+B,ABA + B , A - B , and ABA B all exist. What can you conclude about the dimensions of A\mathrm { A } and B\mathrm { B } ?

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Graph the solution set of the system of inequalities. - y\leq--6x-4 y\geq+6x+4  Graph the solution set of the system of inequalities. - \begin{array} { l }  y \leq - x ^ { 2 } - 6 x - 4 \\ y \geq x ^ { 2 } + 6 x + 4 \end{array}

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Solve the problem using matrices. -In a study of heat transfer in a grid of wires, the temperature at an exterior node is maintained at a constant value (in F{ } ^ { \circ } \mathrm { F } ) as shown in the figure. When the grid is in thermal equilibrium, the temperature at an interior node is the average of the temperatures at the four adjacent nodes. For instance T1=0+0+300+T24T _ { 1 } = \frac { 0 + 0 + 300 + T _ { 2 } } { 4 } , or 4T1T2=3004 T _ { 1 } - T _ { 2 } = 300 . Find the temperatures T1,T2T _ { 1 } , T _ { 2 } , and T3T _ { 3 } when the grid is in thermal equilibrium.  Solve the problem using matrices. -In a study of heat transfer in a grid of wires, the temperature at an exterior node is maintained at a constant value (in  { } ^ { \circ } \mathrm { F }  ) as shown in the figure. When the grid is in thermal equilibrium, the temperature at an interior node is the average of the temperatures at the four adjacent nodes. For instance  T _ { 1 } = \frac { 0 + 0 + 300 + T _ { 2 } } { 4 } , or  4 T _ { 1 } - T _ { 2 } = 300 . Find the temperatures  T _ { 1 } , T _ { 2 } , and  T _ { 3 }  when the grid is in thermal equilibrium.

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Provide an appropriate response. -Describe the characteristics of an augmented matrix in diagonal or reduced-row echelon form. 141)

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Provide an appropriate response. -What is the value of mnp000qrs\left| \begin{array} { l l l } \mathrm { m } & \mathrm { n } & \mathrm { p } \\0 & 0 & 0 \\\mathrm { q } & \mathrm { r } & \mathrm { s }\end{array} \right| for any values of the variables?

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Solve the system in terms of the arbitrary variable x. - x-6y+z=10 6x-y-z=18

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Use a graphing calculator and the method of matrix inverses to Give five decimal places, if necessary. -A company makes 3 types of cable. Cable A requires 3 black, 3 white, and 2 red wires. B requires 1 black, 2 white, and 1 red. C requires 2 black, 1 white, and 2 red. The company used 95 black, 100 white and 90 red wires. How many of each type of cable were made?

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Solve the problem. -A $178,000\$ 178,000 trust is to be invested in bonds paying 7%7 \% , CDs paying 6%6 \% , and mortgages paying 9%9 \% . The bond and CD investment together must equal the mortgage investment. To earn a $13,750\$ 13,750 annual income from the investments, how much should the bank invest in bonds?

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Use the Gauss-Jordan method to solve the system of equations. If the system has infinitely many solutions, give the solution with y arbitrary. - 4x+3y=1 2x+4y=8

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Write the augmented matrix for the system. Do not - 5x+5y+7z=23 -2x+9y+4z=6 2x+5y+2z=16

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Solve the linear programming problem. -A summer camp wants to hire counselors and aides to fill its staffing needs at minimum cost. The average monthly salary of a counselor is $2400, and the average monthly salary of an aide is $1100. The camp can accommodate up to 35 staff members and needs at least 20 to run properly. The Camp must have at least 10 aides and may have up to 3 aides for every 2 counselors. How many Counselors and how many aides should the camp hire to minimize cost?

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Find the partial fraction decomposition for the rational expression. - x2x2+6x+9\frac { x ^ { 2 } } { x ^ { 2 } + 6 x + 9 }

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If the system has infinitely many solutions, write the solution set with x arbitrary. - 7x-6y=1 -14x+12y=1

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Find the partial fraction decomposition for the rational expression. - 4x3+8x2+5x72x2x1\frac { 4 x ^ { 3 } + 8 x ^ { 2 } + 5 x - 7 } { 2 x ^ { 2 } - x - 1 }

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Find the values of the variables for which the statement is true, if possible. - [2b4]+[a8c]=[514]\left[ \begin{array} { l l l } - 2 & b & 4 \end{array} \right] + \left[ \begin{array} { l l l } a & 8 & c \end{array} \right] = \left[ \begin{array} { l l l } 5 & - 1 & 4 \end{array} \right]

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Solve the system by substitution. - -2x=5y+19 -31=6y-3x

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