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Solve the system of equations
\n" ); document.write( "3x+4y+z=7
\n" ); document.write( "2y+z=3
\n" ); document.write( "-5x+3y+8z=-31
\n" ); document.write( "**
\n" ); document.write( "1) 3x+4y+z=7
\n" ); document.write( "2) 2y+z=3
\n" ); document.write( "3) -5x+3y+8z=-31
\n" ); document.write( "..
\n" ); document.write( "1) 3x+4y+z=7
\n" ); document.write( "2) 2y+z=3
\n" ); document.write( "4) 3x+2y=4 (subtract eq 2 from eq 1, eliminating z)
\n" ); document.write( "..
\n" ); document.write( "5) 24x+32y+8z=56 (multiply eq 1 by 8)
\n" ); document.write( "3) -5x+3y+8z=-31
\n" ); document.write( "6) 29x+29y=87 (subtract eq 3 from eq 5, eliminating z)
\n" ); document.write( "4) 3x+2y=4
\n" ); document.write( "..
\n" ); document.write( "7) 58x+58y=174 (multiply eq 6 by 2)
\n" ); document.write( "8) 87x+58y=116 (multiply eq 4 by 29)
\n" ); document.write( "9) -29x=58 (subtract eq 8 from eq 7, eliminating y)
\n" ); document.write( "x=-2
\n" ); document.write( "..
\n" ); document.write( "4) 3x+2y=4
\n" ); document.write( "2y=4-3x=4+6=10
\n" ); document.write( "y=5
\n" ); document.write( "..
\n" ); document.write( "3) -5x+3y+8z=-31
\n" ); document.write( "10+15+8z=-31
\n" ); document.write( "8z=-31-25=-56
\n" ); document.write( "z=-7
\n" ); document.write( "..
\n" ); document.write( "Check:
\n" ); document.write( "1) 3x+4y+z=3(-2)+4(5)-7=20-13=7
\n" ); document.write( "2) 2y+z=3=2(5)-7=3
\n" ); document.write( "3) -5x+3y+8z=-5(-2)+3(5)+(8)(-7)=10+15-56=-56+25=-31 \n" ); document.write( "