document.write( "Question 380278: Can you help me solve the system of equations using matrices: x-2y+3z=7 2x+y+z=5 -3x+2y-2z=-10 \n" ); document.write( "
Algebra.Com's Answer #269889 by Jk22(389)\"\" \"About 
You can put this solution on YOUR website!
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Solved by pluggable solver: Using Cramer's Rule to Solve Systems with 3 variables

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\n" ); document.write( " \"system%281%2Ax%2B-2%2Ay%2B3%2Az=7%2C2%2Ax%2B1%2Ay%2B1%2Az=5%2C-3%2Ax%2B2%2Ay%2B-2%2Az=-10%29\"
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\n" ); document.write( " First let \"A=%28matrix%283%2C3%2C1%2C-2%2C3%2C2%2C1%2C1%2C-3%2C2%2C-2%29%29\". This is the matrix formed by the coefficients of the given system of equations.
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\n" ); document.write( " Take note that the right hand values of the system are \"7\", \"5\", and \"-10\" and they are highlighted here:
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\n" ); document.write( " These values are important as they will be used to replace the columns of the matrix A.
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\n" ); document.write( " Now let's calculate the the determinant of the matrix A to get \"abs%28A%29=15\". 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.
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\n" ); document.write( " Notation note: \"abs%28A%29\" denotes the determinant of the matrix A.
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\n" ); document.write( " 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).
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\n" ); document.write( " 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.
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\n" ); document.write( " 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=%2832%29%2F%2815%29=32%2F15\"
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\n" ); document.write( " So the first solution is \"x=32%2F15\"
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\n" ); document.write( " We'll follow the same basic idea to find the other two solutions. Let's reset by letting \"A=%28matrix%283%2C3%2C1%2C-2%2C3%2C2%2C1%2C1%2C-3%2C2%2C-2%29%29\" again (this is the coefficient matrix).
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\n" ); document.write( " 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).
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\n" ); document.write( " Now compute the determinant of \"A%5By%5D\" to get \"abs%28A%5By%5D%29=-8\".
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\n" ); document.write( " 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=%28-8%29%2F%2815%29=-8%2F15\"
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\n" ); document.write( " So the second solution is \"y=-8%2F15\"
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\n" ); document.write( " Let's reset again by letting \"A=%28matrix%283%2C3%2C1%2C-2%2C3%2C2%2C1%2C1%2C-3%2C2%2C-2%29%29\" which is the coefficient matrix.
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\n" ); document.write( " 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\"
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\n" ); document.write( " Now compute the determinant of \"A%5Bz%5D\" to get \"abs%28A%5Bz%5D%29=19\".
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\n" ); document.write( " 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=%2819%29%2F%2815%29=19%2F15\"
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\n" ); document.write( " So the third solution is \"z=19%2F15\"
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\n" ); document.write( " Final Answer:
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\n" ); document.write( " So the three solutions are \"x=32%2F15\", \"y=-8%2F15\", and \"z=19%2F15\" giving the ordered triple (32/15, -8/15, 19/15)
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\n" ); document.write( " 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.
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\n" ); document.write( "\n" ); document.write( "det(A) is \n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
Solved by pluggable solver: Finding the Determinant of a 3x3 Matrix

If you have the general 3x3 matrix:

\"%28matrix%283%2C3%2Ca%2Cb%2Cc%2Cd%2Ce%2Cf%2Cg%2Ch%2Ci%29%29\"

the determinant is:

Which further breaks down to:



Note: \"abs%28matrix%282%2C2%2Ce%2Cf%2Ch%2Ci%29%29\", \"abs%28matrix%282%2C2%2Cd%2Cf%2Cg%2Ci%29%29\" and \"abs%28matrix%282%2C2%2Cd%2Ce%2Cg%2Ch%29%29\" are determinants themselves.
If you need help finding the determinant of 2x2 matrices (which is required to find the determinant of 3x3 matrices), check out this solver

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From the matrix \"%28matrix%283%2C3%2C1%2C-2%2C3%2C2%2C1%2C1%2C-3%2C2%2C-2%29%29\", we can see that \"a=1\", \"b=-2\", \"c=3\", \"d=2\", \"e=1\", \"f=1\", \"g=-3\", \"h=2\", and \"i=-2\"

Start with the general 3x3 determinant.

Plug in the given values (see above)

Multiply

Subtract

\"abs%28matrix%283%2C3%2C1%2C-2%2C3%2C2%2C1%2C1%2C-3%2C2%2C-2%29%29=-4-2%2B21\" Multiply

\"abs%28matrix%283%2C3%2C1%2C-2%2C3%2C2%2C1%2C1%2C-3%2C2%2C-2%29%29=15\" Combine like terms.


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Answer:

So \"abs%28matrix%283%2C3%2C1%2C-2%2C3%2C2%2C1%2C1%2C-3%2C2%2C-2%29%29=15\", which means that the determinant of the matrix \"%28matrix%283%2C3%2C1%2C-2%2C3%2C2%2C1%2C1%2C-3%2C2%2C-2%29%29\" is 15

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\n" ); document.write( "\n" ); document.write( "det(Ax) is \n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
Solved by pluggable solver: Finding the Determinant of a 3x3 Matrix

If you have the general 3x3 matrix:

\"%28matrix%283%2C3%2Ca%2Cb%2Cc%2Cd%2Ce%2Cf%2Cg%2Ch%2Ci%29%29\"

the determinant is:

Which further breaks down to:



Note: \"abs%28matrix%282%2C2%2Ce%2Cf%2Ch%2Ci%29%29\", \"abs%28matrix%282%2C2%2Cd%2Cf%2Cg%2Ci%29%29\" and \"abs%28matrix%282%2C2%2Cd%2Ce%2Cg%2Ch%29%29\" are determinants themselves.
If you need help finding the determinant of 2x2 matrices (which is required to find the determinant of 3x3 matrices), check out this solver

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From the matrix \"%28matrix%283%2C3%2C7%2C-2%2C3%2C5%2C1%2C1%2C-10%2C2%2C-2%29%29\", we can see that \"a=7\", \"b=-2\", \"c=3\", \"d=5\", \"e=1\", \"f=1\", \"g=-10\", \"h=2\", and \"i=-2\"

Start with the general 3x3 determinant.

Plug in the given values (see above)

Multiply

Subtract

\"abs%28matrix%283%2C3%2C7%2C-2%2C3%2C5%2C1%2C1%2C-10%2C2%2C-2%29%29=-28-0%2B60\" Multiply

\"abs%28matrix%283%2C3%2C7%2C-2%2C3%2C5%2C1%2C1%2C-10%2C2%2C-2%29%29=32\" Combine like terms.


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Answer:

So \"abs%28matrix%283%2C3%2C7%2C-2%2C3%2C5%2C1%2C1%2C-10%2C2%2C-2%29%29=32\", which means that the determinant of the matrix \"%28matrix%283%2C3%2C7%2C-2%2C3%2C5%2C1%2C1%2C-10%2C2%2C-2%29%29\" is 32

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\n" ); document.write( "\n" ); document.write( "det(Ay) is \n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
Solved by pluggable solver: Finding the Determinant of a 3x3 Matrix

If you have the general 3x3 matrix:

\"%28matrix%283%2C3%2Ca%2Cb%2Cc%2Cd%2Ce%2Cf%2Cg%2Ch%2Ci%29%29\"

the determinant is:

Which further breaks down to:



Note: \"abs%28matrix%282%2C2%2Ce%2Cf%2Ch%2Ci%29%29\", \"abs%28matrix%282%2C2%2Cd%2Cf%2Cg%2Ci%29%29\" and \"abs%28matrix%282%2C2%2Cd%2Ce%2Cg%2Ch%29%29\" are determinants themselves.
If you need help finding the determinant of 2x2 matrices (which is required to find the determinant of 3x3 matrices), check out this solver

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From the matrix \"%28matrix%283%2C3%2C1%2C7%2C3%2C2%2C5%2C1%2C-3%2C-10%2C-2%29%29\", we can see that \"a=1\", \"b=7\", \"c=3\", \"d=2\", \"e=5\", \"f=1\", \"g=-3\", \"h=-10\", and \"i=-2\"

Start with the general 3x3 determinant.

Plug in the given values (see above)

Multiply

Subtract

\"abs%28matrix%283%2C3%2C1%2C7%2C3%2C2%2C5%2C1%2C-3%2C-10%2C-2%29%29=0--7%2B-15\" Multiply

\"abs%28matrix%283%2C3%2C1%2C7%2C3%2C2%2C5%2C1%2C-3%2C-10%2C-2%29%29=-8\" Combine like terms.


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Answer:

So \"abs%28matrix%283%2C3%2C1%2C7%2C3%2C2%2C5%2C1%2C-3%2C-10%2C-2%29%29=-8\", which means that the determinant of the matrix \"%28matrix%283%2C3%2C1%2C7%2C3%2C2%2C5%2C1%2C-3%2C-10%2C-2%29%29\" is -8

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Solved by pluggable solver: Finding the Determinant of a 3x3 Matrix

If you have the general 3x3 matrix:

\"%28matrix%283%2C3%2Ca%2Cb%2Cc%2Cd%2Ce%2Cf%2Cg%2Ch%2Ci%29%29\"

the determinant is:

Which further breaks down to:



Note: \"abs%28matrix%282%2C2%2Ce%2Cf%2Ch%2Ci%29%29\", \"abs%28matrix%282%2C2%2Cd%2Cf%2Cg%2Ci%29%29\" and \"abs%28matrix%282%2C2%2Cd%2Ce%2Cg%2Ch%29%29\" are determinants themselves.
If you need help finding the determinant of 2x2 matrices (which is required to find the determinant of 3x3 matrices), check out this solver

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From the matrix \"%28matrix%283%2C3%2C1%2C-2%2C7%2C2%2C1%2C5%2C-3%2C2%2C-10%29%29\", we can see that \"a=1\", \"b=-2\", \"c=7\", \"d=2\", \"e=1\", \"f=5\", \"g=-3\", \"h=2\", and \"i=-10\"

Start with the general 3x3 determinant.

Plug in the given values (see above)

Multiply

Subtract

\"abs%28matrix%283%2C3%2C1%2C-2%2C7%2C2%2C1%2C5%2C-3%2C2%2C-10%29%29=-20-10%2B49\" Multiply

\"abs%28matrix%283%2C3%2C1%2C-2%2C7%2C2%2C1%2C5%2C-3%2C2%2C-10%29%29=19\" Combine like terms.


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Answer:

So \"abs%28matrix%283%2C3%2C1%2C-2%2C7%2C2%2C1%2C5%2C-3%2C2%2C-10%29%29=19\", which means that the determinant of the matrix \"%28matrix%283%2C3%2C1%2C-2%2C7%2C2%2C1%2C5%2C-3%2C2%2C-10%29%29\" is 19
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