# Questions on Algebra: Matrices, determinant, Cramer rule answered by real tutors!

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 Algebra: Matrices, determinant, Cramer rule Solvers Lessons Answers archive Quiz In Depth

 Question 345628: For questions 20 and 21, use the matrices below: A=[17 2 3/11 4 -9] B=[10 6 -7/-4 3 0] C=[-1/2/-2] Find A-B Find BC, if possible Please show work. Thank you so much for all of your help!!! Click here to see answer by Fombitz(13828)

 Question 345644: Evaluate: |12 5 -2/ -3 0 1/ -5 4 2| Please show work. Thank you so much for all of your help!!!! Click here to see answer by Fombitz(13828)

 Question 345654: Evaluate: |12 5 -2/ -3 0 1/ -5 4 2| Thank you so much!!! Click here to see answer by jim_thompson5910(28598)

 Question 345680: Need help with systems of equations using matrices. Don't know how to set up this problem. A change machine contains nickels, dimes, and quarters. There are 75 coins in the machine and the value of the coins is \$7.25. If there are 5 times as many nickels as dimes, find the number of coins of each type in the machine. Need by 9pm tonight (if possible). Thank you for your time. Click here to see answer by ankor@dixie-net.com(15667)

 Question 345687: determine the equation of a line passing through the points (1,6) and (-3,-10) using matrix equation. Click here to see answer by Fombitz(13828)

 Question 346098: I need to find the intersecting points of two equations: y=.15x and y=.2(x-20)and graph them. I have included my problem and what is expected. I'm lost. Ok this is what I got : You would set the two equations equal to each other and solve for x .15x=.2(x-20) using the Elimination Method Reorder the terms: 0.15x = 0.2(-20 + x) 0.15x = (-20 * 0.2 + x * 0.2) 0.15x = (-4 + 0.2x) Solving 0.15x = -4 + 0.2x Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.2x' to each side of the equation. 0.15x + -0.2x = -4 + 0.2x + -0.2x Combine like terms: 0.15x + -0.2x = -0.05x -0.05x = -4 + 0.2x + -0.2x Combine like terms: 0.2x + -0.2x = 0.0 -0.05x = -4 + 0.0 -0.05x = -4 Divide each side by '-0.05'. x = 80 Simplifying x = 80 Now that X = 80, I plugged it into the equation y=0.15x and got this: y=0.15x y=0.15(80) y= 12 Now this is the question to my problem and I do not know how to get the answer. I have to graph this and show the intersection. a teacher is looking for the best option in purchasing school supplies for a classroom. Where Company A is offering a discount for every dollar amount spent on school supplies and where Company B is offering a higher discount than Company A, but the discount for Company B is only offered for every dollar amount spent above \$20.00. I will determine and explain which company will offer a better price based upon the dollar amount the teacher spends on school supplies. Option 1- Company A will offer her a 15% discount on the total amount spent in the store. Option 2- Company B will offer her a 20% discount on the remaining amount after the first \$20 is spent. Depict the situation graphically, using appropriate graphing software such as Excel or an online graphing utility. Include the following in your graph: • A depiction of each cost option on the same graph • Clear labels of the cost to the hypothetical customer for both options on the graph • The intersection of the cost options (if one exists) I'm so lost. I do not know how to graph this. Please help if you can. Click here to see answer by Fombitz(13828)
 Question 346098: I need to find the intersecting points of two equations: y=.15x and y=.2(x-20)and graph them. I have included my problem and what is expected. I'm lost. Ok this is what I got : You would set the two equations equal to each other and solve for x .15x=.2(x-20) using the Elimination Method Reorder the terms: 0.15x = 0.2(-20 + x) 0.15x = (-20 * 0.2 + x * 0.2) 0.15x = (-4 + 0.2x) Solving 0.15x = -4 + 0.2x Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.2x' to each side of the equation. 0.15x + -0.2x = -4 + 0.2x + -0.2x Combine like terms: 0.15x + -0.2x = -0.05x -0.05x = -4 + 0.2x + -0.2x Combine like terms: 0.2x + -0.2x = 0.0 -0.05x = -4 + 0.0 -0.05x = -4 Divide each side by '-0.05'. x = 80 Simplifying x = 80 Now that X = 80, I plugged it into the equation y=0.15x and got this: y=0.15x y=0.15(80) y= 12 Now this is the question to my problem and I do not know how to get the answer. I have to graph this and show the intersection. a teacher is looking for the best option in purchasing school supplies for a classroom. Where Company A is offering a discount for every dollar amount spent on school supplies and where Company B is offering a higher discount than Company A, but the discount for Company B is only offered for every dollar amount spent above \$20.00. I will determine and explain which company will offer a better price based upon the dollar amount the teacher spends on school supplies. Option 1- Company A will offer her a 15% discount on the total amount spent in the store. Option 2- Company B will offer her a 20% discount on the remaining amount after the first \$20 is spent. Depict the situation graphically, using appropriate graphing software such as Excel or an online graphing utility. Include the following in your graph: • A depiction of each cost option on the same graph • Clear labels of the cost to the hypothetical customer for both options on the graph • The intersection of the cost options (if one exists) I'm so lost. I do not know how to graph this. Please help if you can. Click here to see answer by mananth(12270)

 Question 346215: How do I find the inverse of [5 3] [7 9]? (That's supposed to be a matrix, I didn't know how to make one on here) So far I have gotten the determinant of 21 but I don't remember what to do from there. Thanks Click here to see answer by Fombitz(13828)

 Question 346964: 6(2/3[2 3 1/2[-4 2 6 -5 3 0 -1 0]+ 1 -8]) this is the best i can do i hope you can read it. Click here to see answer by haileytucki(390)

 Question 347420: solve the following equation.. 0 0-1 3 x 0 =x^2 2 0 3 Click here to see answer by fractalier(2101)

 Question 347425: find the sum of the following matrices 2 0 3 -3 + 0 -3 -3 8 Click here to see answer by jim_thompson5910(28598)

 Question 347423: find the product of 2 3 5 0 1 2 x 4 2 -1 0 -3 2 Click here to see answer by jim_thompson5910(28598)

 Question 347506: given the matrix A= 2 3 0 -1 1 4 what are its dimensions? Click here to see answer by Fombitz(13828)
 Question 347506: given the matrix A= 2 3 0 -1 1 4 what are its dimensions? Click here to see answer by jsmallt9(3296)

 Question 347565: solve the system using eliminaton or sustitution -3x+y-z=-2 2x-y-2z=-12 4x+2y+z=1 Click here to see answer by haileytucki(390)

 Question 347597: 1.(a)given the matrix=A {2 3},what ar its dimension {0-1} {1 4} b)can these matrices be multiplied,why or why not? {2} {3 0} {4} {-2 3} {0} {1 2} Click here to see answer by Edwin McCravy(8921)
 Question 347597: 1.(a)given the matrix=A {2 3},what ar its dimension {0-1} {1 4} b)can these matrices be multiplied,why or why not? {2} {3 0} {4} {-2 3} {0} {1 2} Click here to see answer by Fombitz(13828)

 Question 347692: can you please help me with this word problem? I am suppose to write equations for this word problem and they are suppose to fit in a matrix. Word Problem: The senior class is selling greeting cards. Birthday Cards sell for \$5.00 a box. Thank You cards sell for \$7.00 a box. You sold 4 more boxes of birthday cards than thank you cards. your total sales was \$152.00. How many Boxes of each kind did you sell? Thank you Click here to see answer by stanbon(57424)

 Question 348226: Please help me solve this equation: Express each of the following systems of equations in the standard multiplicative form and in the augmented matrix form. a) , , , b) , , , Click here to see answer by Edwin McCravy(8921)

 Question 349041: I need help solving this equation from my algebra 2 class. it is a 3x3 matrix set equal to x^2. The instructions I've been given say, "Solve the equation." the problem is as follows: 0 0 -1 3 x 0 2 0 3 equal to x^2 Click here to see answer by mananth(12270)

 Question 349287: Find values of x and y, if any, that will make the two matrices equal. x y 2 5 1 3 = 1 3 Click here to see answer by stanbon(57424)

 Question 349960: Please help me with this, same question is on the test tomorrow according to the prof. Thank you so much Solve using Gauss-Jordan Elimination: As the school psychologist, you are consulting with the staff nutritionist about one of your student's low energy and propensity for minor illness. the nutritionist has suggested a daily routine of 350 units of vitamin C, 4200 units of Vitamin A, and 400 units of Vitamin D. She also recommends the following sources of these vitamins: Megadose Supra contains 50 units of C, 1000 units of A, and 100 units of D per capsule. Crazy Caps contains 100 units of C, 200 units of A, and 100 units of D. Formula I contains 50 units of C, 500 units of A and no Vitamin D per capsule. How many of each capsule should the student take to get the recommended dosages? Click here to see answer by solver91311(16897)

 Question 350085: suppose A is a 2 x 2 matrix as follows A = [56 34] how do i decide whether A is invertible? and if it is find A^-1 Click here to see answer by Fombitz(13828)

 Question 350511: (a)If A is idempotent and has an inverse A^(-1) show that A=I Explain what this result says about the kinds of matrices that could possibly be both invertible and idempotent. (b) If A is idempotent, does it have to be square? Why or why not? (c) Let B=[1 0 0 0] Is B idempotent? Click here to see answer by jim_thompson5910(28598)

 Question 350586: suppose A is a 3x3 matrix with elements a11 =1 a12=0 a13=2 a21=-1 a22=3 a23=4 a31=0 a32=1 a33=0 how would you use A^-1 to find the solutions of the linear system x+2z = 1 and -x+3y+4z =2 and y=3 could you please show working. i have used numbers with subscripts to depict the matrix entries because i dont know how to type the brackets Click here to see answer by Fombitz(13828)

 Question 351570: solve this problem through cramer's rule y-x=1 3y+x=6 Click here to see answer by ewatrrr(10682)

 Question 353075: Hello I am having problems in solving the eigenvectors for the matrix: 3 0 8 -1 I have already calculated the eigenvalues which are -1 and 3 but I can not get the eigenvector, because of the zero in the top right hand corner. Any help is much appreciated Iman Click here to see answer by Fombitz(13828)

 Question 353443: What does X, Y and Z equal if the system equation is: 2x-3y+=1 x+y+2z=3 3x-2y+2z=3 Click here to see answer by Fombitz(13828)

 Question 354811: When I enter my matrix it doesn't give the right answer. It doesn't have a spot for me to put the complete problem. Here is just one of my problems. 5x+2y=-4 4x-3y-17 Click here to see answer by stanbon(57424)