document.write( "Question 135991: I have another question. My professor wants us to solve these equations in four different ways and show our work. I have been able to do the simpler equations but when they have 3 or 4 variables it gets a little bit more complicated.\r
\n" ); document.write( "\n" ); document.write( "I need to use the elimination method, substitution method, determinant and coordinates for example if if x=0 y=-5 etc...\r
\n" ); document.write( "\n" ); document.write( "Here are two problems that I'm having a hard time with.\r
\n" ); document.write( "\n" ); document.write( "#5
\n" ); document.write( "x+y+z=6
\n" ); document.write( "2x-y+3z=9
\n" ); document.write( "-x+2y+z=6\r
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\n" ); document.write( "\n" ); document.write( "#7
\n" ); document.write( "3x+2y+z=6
\n" ); document.write( "2x-y+4z=-4
\n" ); document.write( "x+y-2z=5\r
\n" ); document.write( "\n" ); document.write( "Each one has to be done in four different ways. Thanks again for all the help.\r
\n" ); document.write( "\n" ); document.write( "Anne\r
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Algebra.Com's Answer #99660 by solver91311(24713)\"\" \"About 
You can put this solution on YOUR website!
When you say 'coordinate' method, do you mean to solve the system by graphing? I certainly hope not because there is no way to render a three-dimensional coordinate system on this site. However, I'll do one of your systems by the other three methods.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "1. \"x%2By%2Bz=6\"
\n" ); document.write( "2. \"2x-y%2B3z=9\"
\n" ); document.write( "3. \"-x%2B2y%2Bz=6\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Elimination:
\n" ); document.write( "Replace Eq. 2 with the sum of Eq. 2 and two times Eq. 3.
\n" ); document.write( "Replace Eq. 3 with the sum of Eq. 1 and Eq. 3.
\n" ); document.write( "1. \"x%2By%2Bz=6\"
\n" ); document.write( "2. \"0x%2B3y%2B5z=21\"
\n" ); document.write( "3. \"0x%2B3y%2B2z=12\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Replace Eq. 3 with the sum of Eq. 2 and -1 times Eq. 3.
\n" ); document.write( "1. \"x%2By%2Bz=6\"
\n" ); document.write( "2. \"0x%2B3y%2B5z=21\"
\n" ); document.write( "3. \"0x%2B0y%2B3z=9\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Divide Eq 3 by 3
\n" ); document.write( "1. \"x%2By%2Bz=6\"
\n" ); document.write( "2. \"0x%2B3y%2B5z=21\"
\n" ); document.write( "3. \"0x%2B0y%2Bz=3\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Replace Eq. 1 with the sum of Eq. 1 and -1 times Eq. 3
\n" ); document.write( "Replace Eq. 2 with the sum of Eq. 2 and -5 times Eq. 3
\n" ); document.write( "1. \"x%2By%2B0z=3\"
\n" ); document.write( "2. \"0x%2B3y%2B0z=6\"
\n" ); document.write( "3. \"0x%2B0y%2Bz=3\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Divide Eq. 2 by 3
\n" ); document.write( "1. \"x%2By%2B0z=3\"
\n" ); document.write( "2. \"0x%2By%2B0z=2\"
\n" ); document.write( "3. \"0x%2B0y%2Bz=3\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Replace Eq. 1 with the sum of Eq. 1 and -1 times Eq. 2
\n" ); document.write( "1. \"x%2B0y%2B0z=1\"
\n" ); document.write( "2. \"0x%2By%2B0z=2\"
\n" ); document.write( "3. \"0x%2B0y%2Bz=3\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Eliminate the variables with zero coefficients
\n" ); document.write( "1. \"x=1\"
\n" ); document.write( "2. \"y=2\"
\n" ); document.write( "3. \"z=3\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "========================================================
\n" ); document.write( "Substitution:\r
\n" ); document.write( "\n" ); document.write( "1. \"x%2By%2Bz=6\"
\n" ); document.write( "2. \"2x-y%2B3z=9\"
\n" ); document.write( "3. \"-x%2B2y%2Bz=6\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Solve Eq. 1 for x:
\n" ); document.write( "\"x=6-y-z\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Substitute the expression for x into the other two equations
\n" ); document.write( "2. \"2%286-y-z%29-y%2B3z=9\"
\n" ); document.write( "3. \"-%286-y-z%29%2B2y%2Bz=6\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Distribute and collect like terms:
\n" ); document.write( "2. \"12-2y-2z-y%2B3z=9\" => \"-3y%2Bz=-3\" (New Eq. 2)\r
\n" ); document.write( "\n" ); document.write( "3. \"-6%2By%2Bz%2B2y%2Bz=6\" => \"3y%2B2z=12\" (New Eq. 3)\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Solve equation 2 for y:
\n" ); document.write( "\"-3y=-3-z\"
\n" ); document.write( "\"y=1%2B%28z%2F3%29\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Substitute this expression for y into the new Eq. 3
\n" ); document.write( "\"3%281%2Bz%2F3%29%2B2z=12\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Distribute, simplify, collect terms
\n" ); document.write( "\"3%2B3z%2F3%2B2z=12\"
\n" ); document.write( "\"z%2B2z=12-3\"
\n" ); document.write( "\"3z=9\"
\n" ); document.write( "\"z=3\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Substitute this value for z into the new Eq. 2
\n" ); document.write( "\"-3y%2B3=-3\"
\n" ); document.write( "\"-3y=-6\"
\n" ); document.write( "\"y=2\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Substitute the values for y and z into the original equation 1:
\n" ); document.write( "\"x%2By%2Bz=6\"
\n" ); document.write( "\"x%2B2%2B3=6\"
\n" ); document.write( "\"x=1\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "============================================================
\n" ); document.write( "Cramer's Rule\r
\n" ); document.write( "\n" ); document.write( "Create and evaluate the coefficient determinant\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "D =\"%28matrix%283%2C3%2C1%2C1%2C1%2C2%2C-1%2C3%2C-1%2C2%2C1%29%29\"\r
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\n" ); document.write( "\n" ); document.write( "If you don't remember how to evaluate a determinant, here is a little cartoon that shows the process. You have to take your coefficient determinant and make a 5X3 matrix by repeating the 1st and 2nd columns first. Then follow the process shown:\r
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\n" ); document.write( "\n" ); document.write( "\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Yours evaluates to: -9, so we say \"D=-9\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Next, replace the first column representing the coefficients on the x terms with the constant term values.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"D%5Bx%5D=%28matrix%283%2C3%2C6%2C1%2C1%2C9%2C-1%2C3%2C6%2C2%2C1%29%29\", and do the determinant evaluation on t\"D%5Bx%5D\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "This works out to -9 as well, so you can say \"D%5Bx%5D=-9\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Cramer's rule says:\r
\n" ); document.write( "\n" ); document.write( "\"x=D%5Bx%5D%2FD\". In this case: \"-9%2F-9=1\" (Just as I most sincerely hope you expected)\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "As you might suspect, you replace the second column with the coefficients to get \"D%5By%5D\" and the third column to get \"D%5Bz%5D\".\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Then \"y=D%5By%5D%2FD\" and \"z=D%5Bz%5D%2FD\"\r
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\n" ); document.write( "\n" ); document.write( "I'll give you the \"D%5By%5D\" and \"D%5Bz%5D\" matrices and you can do the calculations for yourself.\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"D%5By%5D=%28matrix%283%2C3%2C1%2C6%2C1%2C2%2C9%2C3%2C-1%2C6%2C1%29%29\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"D%5Bz%5D=%28matrix%283%2C3%2C1%2C1%2C6%2C2%2C-1%2C9%2C-1%2C2%2C6%29%29\"\r
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