document.write( "Question 474514: Solve the following Using Cramer's rule\r
\n" ); document.write( "\n" ); document.write( "1.) 8x+5y=7
\n" ); document.write( " 6x-7y=59\r
\n" ); document.write( "\n" ); document.write( "2.) 3x-7y=34
\n" ); document.write( " 8x+9y=-20\r
\n" ); document.write( "\n" ); document.write( "3.) 3x-2y+2z=0
\n" ); document.write( " 4x+3y-z=-15
\n" ); document.write( " 2x+5y+4z=-10
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Algebra.Com's Answer #325447 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!
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\n" ); document.write( "\n" ); document.write( "1.) \"8x%2B5y=7\"
\n" ); document.write( " \"+6x-7y=59\"\r
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Solved by pluggable solver: Using Cramer's Rule to Solve Systems with 2 variables

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\n" ); document.write( " \"system%288%2Ax%2B5%2Ay=7%2C6%2Ax%2B-7%2Ay=59%29\"
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\n" ); document.write( " First let \"A=%28matrix%282%2C2%2C8%2C5%2C6%2C-7%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\" and \"59\" which are highlighted here:
\n" ); document.write( " \"system%288%2Ax%2B5%2Ay=highlight%287%29%2C6%2Ax%2B-7%2Ay=highlight%2859%29%29\"
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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=%288%29%28-7%29-%285%29%286%29=-86\". Remember that the determinant of the 2x2 matrix \"A=%28matrix%282%2C2%2Ca%2Cb%2Cc%2Cd%29%29\" is \"abs%28A%29=ad-bc\". If you need help with calculating the determinant of any two by two matrices, then 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( " \"A%5Bx%5D=%28matrix%282%2C2%2Chighlight%287%29%2C5%2Chighlight%2859%29%2C-7%29%29\"
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\n" ); document.write( " Now compute the determinant of \"A%5Bx%5D\" to get \"abs%28A%5Bx%5D%29=%287%29%28-7%29-%285%29%2859%29=-344\". Once again, remember that the determinant of the 2x2 matrix \"A=%28matrix%282%2C2%2Ca%2Cb%2Cc%2Cd%29%29\" is \"abs%28A%29=ad-bc\"
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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=%28-344%29%2F%28-86%29=4\"
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\n" ); document.write( " So the first solution is \"x=4\"
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\n" ); document.write( " We'll follow the same basic idea to find the other solution. Let's reset by letting \"A=%28matrix%282%2C2%2C8%2C5%2C6%2C-7%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( " \"A%5Bx%5D=%28matrix%282%2C2%2C8%2Chighlight%287%29%2C6%2Chighlight%2859%29%29%29\"
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\n" ); document.write( " Now compute the determinant of \"A%5By%5D\" to get \"abs%28A%5By%5D%29=%288%29%2859%29-%287%29%286%29=430\".
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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=%28430%29%2F%28-86%29=-5\"
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\n" ); document.write( " So the second solution is \"y=-5\"
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\n" ); document.write( " ====================================================================================
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\n" ); document.write( " Final Answer:
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\n" ); document.write( " So the solutions are \"x=4\" and \"y=-5\" giving the ordered pair (4, -5)
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\n" ); document.write( " Once again, Cramer's Rule is dependent on determinants. Take a look at this 2x2 Determinant Solver if you need more practice with determinants.
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\n" ); document.write( "\n" ); document.write( "2.) \"3x-7y=34\"
\n" ); document.write( " \"8x%2B9y=-20\"\r
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Solved by pluggable solver: Using Cramer's Rule to Solve Systems with 2 variables

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\n" ); document.write( " \"system%283%2Ax%2B-7%2Ay=34%2C8%2Ax%2B9%2Ay=-20%29\"
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\n" ); document.write( "
\n" ); document.write( " First let \"A=%28matrix%282%2C2%2C3%2C-7%2C8%2C9%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 \"34\" and \"-20\" which are highlighted here:
\n" ); document.write( " \"system%283%2Ax%2B-7%2Ay=highlight%2834%29%2C8%2Ax%2B9%2Ay=highlight%28-20%29%29\"
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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=%283%29%289%29-%28-7%29%288%29=83\". Remember that the determinant of the 2x2 matrix \"A=%28matrix%282%2C2%2Ca%2Cb%2Cc%2Cd%29%29\" is \"abs%28A%29=ad-bc\". If you need help with calculating the determinant of any two by two matrices, then 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( " ---------------------------------------------------------
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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( " \"A%5Bx%5D=%28matrix%282%2C2%2Chighlight%2834%29%2C-7%2Chighlight%28-20%29%2C9%29%29\"
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\n" ); document.write( " Now compute the determinant of \"A%5Bx%5D\" to get \"abs%28A%5Bx%5D%29=%2834%29%289%29-%28-7%29%28-20%29=166\". Once again, remember that the determinant of the 2x2 matrix \"A=%28matrix%282%2C2%2Ca%2Cb%2Cc%2Cd%29%29\" is \"abs%28A%29=ad-bc\"
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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=%28166%29%2F%2883%29=2\"
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\n" ); document.write( " So the first solution is \"x=2\"
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\n" ); document.write( " We'll follow the same basic idea to find the other solution. Let's reset by letting \"A=%28matrix%282%2C2%2C3%2C-7%2C8%2C9%29%29\" again (this is the coefficient matrix).
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\n" ); document.write( "
\n" ); document.write( "
\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( " \"A%5Bx%5D=%28matrix%282%2C2%2C3%2Chighlight%2834%29%2C8%2Chighlight%28-20%29%29%29\"
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\n" ); document.write( " Now compute the determinant of \"A%5By%5D\" to get \"abs%28A%5By%5D%29=%283%29%28-20%29-%2834%29%288%29=-332\".
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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=%28-332%29%2F%2883%29=-4\"
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\n" ); document.write( " So the second solution is \"y=-4\"
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\n" ); document.write( " ====================================================================================
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\n" ); document.write( " Final Answer:
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\n" ); document.write( " So the solutions are \"x=2\" and \"y=-4\" giving the ordered pair (2, -4)
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\n" ); document.write( " Once again, Cramer's Rule is dependent on determinants. Take a look at this 2x2 Determinant Solver if you need more practice with determinants.
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\n" ); document.write( "\n" ); document.write( "3.) \"3x-2y%2B2z=0\"
\n" ); document.write( " \"4x%2B3y-z=-15\"
\n" ); document.write( " \"2x%2B5y%2B4z=-10\"\r
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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( " First let \"A=%28matrix%283%2C3%2C3%2C-2%2C2%2C4%2C3%2C-1%2C2%2C5%2C4%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 \"0\", \"-15\", 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=115\". 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=-230\". 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=%28-230%29%2F%28115%29=-2\"
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\n" ); document.write( " So the first solution is \"x=-2\"
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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%2C3%2C-2%2C2%2C4%2C3%2C-1%2C2%2C5%2C4%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=-230\".
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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=%28-230%29%2F%28115%29=-2\"
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\n" ); document.write( " So the second solution is \"y=-2\"
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\n" ); document.write( " Let's reset again by letting \"A=%28matrix%283%2C3%2C3%2C-2%2C2%2C4%2C3%2C-1%2C2%2C5%2C4%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=115\".
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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=%28115%29%2F%28115%29=1\"
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\n" ); document.write( " So the third solution is \"z=1\"
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\n" ); document.write( " Final Answer:
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\n" ); document.write( " So the three solutions are \"x=-2\", \"y=-2\", and \"z=1\" giving the ordered triple (-2, -2, 1)
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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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