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y+z=6
\n" ); document.write( "x+5y-4Z=4
\n" ); document.write( "x-3y+5z=7
\n" ); document.write( ":
\n" ); document.write( "Take the last two equations and eliminate x:
\n" ); document.write( "x + 5y - 4z = 4
\n" ); document.write( "x - 3y + 5z = 7
\n" ); document.write( "----------------subtract
\n" ); document.write( "0x +8y - 9z = -3
\n" ); document.write( ":
\n" ); document.write( "Using the 1st equation for substitution for y in 8y - 9z = -3:
\n" ); document.write( "y + z = 6
\n" ); document.write( " y = (6-z)
\n" ); document.write( ":
\n" ); document.write( "8(6-z) - 9z = -3
\n" ); document.write( "48 - 8z - 9z = - 3
\n" ); document.write( " -17z = -3 -48
\n" ); document.write( " -17z = -51
\n" ); document.write( " z = -51/-17
\n" ); document.write( " z = +3
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Find y using the 1st equation, substituting 3 for z
\n" ); document.write( "y + z = 6
\n" ); document.write( "y + 3 = 6
\n" ); document.write( " y = 6 - 3
\n" ); document.write( " y = + 3 also
\n" ); document.write( ":
\n" ); document.write( "Find x using the 2nd equation, substituting 3 for y and z
\n" ); document.write( "x + 5y - 4z = 4
\n" ); document.write( "x +5(3) - 4(3) = 4
\n" ); document.write( "x + 15 - 12 = 4
\n" ); document.write( "x + 3 = 4
\n" ); document.write( "x = 4 - 3
\n" ); document.write( "x = +1
\n" ); document.write( ":
\n" ); document.write( "Check all three solutions in the 3rd equation:
\n" ); document.write( "x - 3y + 5z = 7
\n" ); document.write( "1 - 3(3) + 5(3) =
\n" ); document.write( "1 - 9 + 15 = 7; seems to be correct
\n" ); document.write( ":
\n" ); document.write( "Make sense to you??
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