document.write( "Question 929967: help solving this sytem of equations?\r
\n" ); document.write( "\n" ); document.write( "5x + 2y - 5z = 31
\n" ); document.write( "2x - 4y + 2z = 6
\n" ); document.write( "4x - 5y + 4z = 6
\n" ); document.write( "

Algebra.Com's Answer #564612 by ewatrrr(24785)\"\" \"About 
You can put this solution on YOUR website!
5x + 2y - 5z = 31
\n" ); document.write( " 2x - 4y + 2z = 6
\n" ); document.write( " 4x - 5y + 4z = 6
\n" ); document.write( " (3, -2, -4)
\n" ); document.write( "\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
Solved by pluggable solver: Using Cramer's Rule to Solve Systems with 3 variables

\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"system%285%2Ax%2B2%2Ay%2B-5%2Az=31%2C2%2Ax%2B-4%2Ay%2B2%2Az=6%2C4%2Ax%2B-5%2Ay%2B4%2Az=6%29\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " First let \"A=%28matrix%283%2C3%2C5%2C2%2C-5%2C2%2C-4%2C2%2C4%2C-5%2C4%29%29\". This is the matrix formed by the coefficients of the given system of equations.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Take note that the right hand values of the system are \"31\", \"6\", and \"6\" and they are highlighted here:
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " These values are important as they will be used to replace the columns of the matrix A.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Now let's calculate the the determinant of the matrix A to get \"abs%28A%29=-60\". 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.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Notation note: \"abs%28A%29\" denotes the determinant of the matrix A.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " ---------------------------------------------------------
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\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).
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Now compute the determinant of \"A%5Bx%5D\" to get \"abs%28A%5Bx%5D%29=-180\". 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.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\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=%28-180%29%2F%28-60%29=3\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the first solution is \"x=3\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " ---------------------------------------------------------
\n" ); document.write( "
\n" ); document.write( "
\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%2C5%2C2%2C-5%2C2%2C-4%2C2%2C4%2C-5%2C4%29%29\" again (this is the coefficient matrix).
\n" ); document.write( "
\n" ); document.write( "
\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).
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Now compute the determinant of \"A%5By%5D\" to get \"abs%28A%5By%5D%29=120\".
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\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=%28120%29%2F%28-60%29=-2\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the second solution is \"y=-2\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " ---------------------------------------------------------
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Let's reset again by letting \"A=%28matrix%283%2C3%2C5%2C2%2C-5%2C2%2C-4%2C2%2C4%2C-5%2C4%29%29\" which is the coefficient matrix.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\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\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Now compute the determinant of \"A%5Bz%5D\" to get \"abs%28A%5Bz%5D%29=240\".
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\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=%28240%29%2F%28-60%29=-4\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the third solution is \"z=-4\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " ====================================================================================
\n" ); document.write( "
\n" ); document.write( " Final Answer:
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So the three solutions are \"x=3\", \"y=-2\", and \"z=-4\" giving the ordered triple (3, -2, -4)
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\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.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" );