document.write( "Question 475310: 2x + 4y + 4z = 16
\n" ); document.write( "2x - y + 3z = 9
\n" ); document.write( "3x + 4y - z = 8
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Algebra.Com's Answer #325930 by ccs2011(207)\"\" \"About 
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I think the best way to do these is using the elimination method.
\n" ); document.write( "Eliminate a variable to break it down into a system of 2 equations, then use elimination again to break it down to a single equation. Solve for that variable and then use substitution to find the 2nd variable in the system of 2 equations. Then substitute both those values into one of the original equations to find 3rd variable.
\n" ); document.write( "Let me label each equation: A,B,C for reference
\n" ); document.write( "A:\"2x+%2B+4y+%2B+4z+=+16\"
\n" ); document.write( "B:\"2x+-+y+%2B+3z+=+9\"
\n" ); document.write( "C:\"3x+%2B+4y+-+z+=+8\"
\n" ); document.write( "Notice A and C both have a 4y, therefore it will be easiest to eliminate variable y. Multiply C by -1. Add A and C. Call the resulting equation D.
\n" ); document.write( "D:\"-x+%2B+5z+=+8\"
\n" ); document.write( "We still need another equation with x and z. To eliminate y again. Multiply B by 4. Add A and B. Call the resulting equation E.
\n" ); document.write( "E:\"10x+%2B+16z+=+52\"
\n" ); document.write( "Now eliminate x. Multiply D by 10. Add D and E.
\n" ); document.write( "\"66z+=+132\"
\n" ); document.write( "Solve for z. Divide by 66 on both sides.
\n" ); document.write( "\"z+=+2\"
\n" ); document.write( "Substitute z=2 into D.
\n" ); document.write( "\"-x+%2B+5%282%29+=+8\"
\n" ); document.write( "Solve for x.
\n" ); document.write( "\"-x+%2B+10+=+8\"
\n" ); document.write( "Subtract 10 on both sides
\n" ); document.write( "\"-x+=+-2\"
\n" ); document.write( "Flip signs
\n" ); document.write( "\"x+=+2\"
\n" ); document.write( "Substitute x=2, z=2 into B.
\n" ); document.write( "\"2%282%29+-+y+%2B+3%282%29+=+9\"
\n" ); document.write( "Solve for y
\n" ); document.write( "\"4+-+y+%2B+6+=+9\"
\n" ); document.write( "\"-y+%2B+10+=+9\"
\n" ); document.write( "Subtract 10 on both sides
\n" ); document.write( "\"-y+=+-1\"
\n" ); document.write( "Flip signs
\n" ); document.write( "\"y+=+1\"
\n" ); document.write( "Verify solution by substituting into other equations A and C.
\n" ); document.write( "\"2%282%29+%2B+4%281%29+%2B+4%282%29+=+16\"
\n" ); document.write( "\"4%2B4%2B8+=+16\"
\n" ); document.write( "\"16+=+16\"
\n" ); document.write( "True...it works.
\n" ); document.write( "\"3%282%29+%2B+4%281%29+-+2+=+8\"
\n" ); document.write( "\"6+%2B+4+-+2=+8\"
\n" ); document.write( "\"8=8\"
\n" ); document.write( "True..it works.
\n" ); document.write( "Solution is x = 2, y = 1, z = 2
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