SOLUTION: I can't figure this matrix system out Solve system using a matrix: r + 2s - t =4 2r + 2s -6t =12 -2r - 2s -2t =4

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Question 1007819: I can't figure this matrix system out
Solve system using a matrix:
r + 2s - t =4
2r + 2s -6t =12
-2r - 2s -2t =4
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

r+%2B+2s+-+t+=4
2r+%2B+2s+-6t+=12
-2r+-+2s+-2t+=4
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Solved by pluggable solver: Using Cramer's Rule to Solve Systems with 3 variables







First let A=%28matrix%283%2C3%2C1%2C2%2C-1%2C2%2C2%2C-6%2C-2%2C-2%2C-2%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 4, 12, and 4 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=16. 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=-32. 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=%28-32%29%2F%2816%29=-2



So the first solution is x=-2




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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%2C1%2C2%2C-1%2C2%2C2%2C-6%2C-2%2C-2%2C-2%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=32.



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=%2832%29%2F%2816%29=2



So the second solution is y=2




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Let's reset again by letting A=%28matrix%283%2C3%2C1%2C2%2C-1%2C2%2C2%2C-6%2C-2%2C-2%2C-2%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=-32.



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=%28-32%29%2F%2816%29=-2



So the third solution is z=-2




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Final Answer:




So the three solutions are x=-2, y=2, and z=-2 giving the ordered triple (-2, 2, -2)




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.




note, your
r=x
s=y
t=z
so, solutions are
r=+-2,
s=2, and
t=+-2+
giving the ordered triple
(-2, 2, -2)