SOLUTION: using cramer's rule for 3*3 2x+4z=5y+28 x+11y=5z-41 3x-3=2y+z

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Question 889603: using cramer's rule for 3*3
2x+4z=5y+28
x+11y=5z-41
3x-3=2y+z

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
2x+4z=5y+28
x+11y=5z-41
3x-3=2y+z
rearrange
2x+4z-5y=28
x+11y-5z=-41
3x-2y-z=3
2,4,-5,28
1,1,-5,-41
3,-2,-1,3


Solved by pluggable solver: Using Cramer's Rule to Solve Systems with 3 variables







First let A=%28matrix%283%2C3%2C2%2C4%2C-5%2C1%2C1%2C-5%2C3%2C-2%2C-1%29%29. This is the matrix formed by the coefficients of the given system of equations.


Take note that the right hand values of the system are 28, -41, and 3 and they are highlighted here:




These values are important as they will be used to replace the columns of the matrix A.




Now let's calculate the the determinant of the matrix A to get abs%28A%29=-53. To save space, I'm not showing the calculations for the determinant. However, if you need help with calculating the determinant of the matrix A, check out this solver.



Notation note: abs%28A%29 denotes the determinant of the matrix A.



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Now replace the first column of A (that corresponds to the variable 'x') with the values that form the right hand side of the system of equations. We will denote this new matrix A%5Bx%5D (since we're replacing the 'x' column so to speak).






Now compute the determinant of A%5Bx%5D to get abs%28A%5Bx%5D%29=-927. Again, as a space saver, I didn't include the calculations of the determinant. Check out this solver to see how to find this determinant.



To find the first solution, simply divide the determinant of A%5Bx%5D by the determinant of A to get: x=%28abs%28A%5Bx%5D%29%29%2F%28abs%28A%29%29=%28-927%29%2F%28-53%29=927%2F53



So the first solution is x=927%2F53




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We'll follow the same basic idea to find the other two solutions. Let's reset by letting A=%28matrix%283%2C3%2C2%2C4%2C-5%2C1%2C1%2C-5%2C3%2C-2%2C-1%29%29 again (this is the coefficient matrix).




Now replace the second column of A (that corresponds to the variable 'y') with the values that form the right hand side of the system of equations. We will denote this new matrix A%5By%5D (since we're replacing the 'y' column in a way).






Now compute the determinant of A%5By%5D to get abs%28A%5By%5D%29=-910.



To find the second solution, divide the determinant of A%5By%5D by the determinant of A to get: y=%28abs%28A%5By%5D%29%29%2F%28abs%28A%29%29=%28-910%29%2F%28-53%29=910%2F53



So the second solution is y=910%2F53




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Let's reset again by letting A=%28matrix%283%2C3%2C2%2C4%2C-5%2C1%2C1%2C-5%2C3%2C-2%2C-1%29%29 which is the coefficient matrix.



Replace the third column of A (that corresponds to the variable 'z') with the values that form the right hand side of the system of equations. We will denote this new matrix A%5Bz%5D






Now compute the determinant of A%5Bz%5D to get abs%28A%5Bz%5D%29=-802.



To find the third solution, divide the determinant of A%5Bz%5D by the determinant of A to get: z=%28abs%28A%5Bz%5D%29%29%2F%28abs%28A%29%29=%28-802%29%2F%28-53%29=802%2F53



So the third solution is z=802%2F53




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Final Answer:




So the three solutions are x=927%2F53, y=910%2F53, and z=802%2F53 giving the ordered triple (927/53, 910/53, 802/53)




Note: there is a lot of work that is hidden in finding the determinants. Take a look at this 3x3 Determinant Solver to see how to get each determinant.