document.write( "Question 773139: I'm stuck on a problem in my algebra test.
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\n" ); document.write( "Solve each system of equations.
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\n" ); document.write( "5x = -15
\n" ); document.write( "-11x - 4y + 7z = 1
\n" ); document.write( "3x - 3y + z = 1
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\n" ); document.write( "A) x=3, y=-19, z=41
\n" ); document.write( "B) x=42, y=-33, z=-13
\n" ); document.write( "C) x=-45, y=-14, z=-40
\n" ); document.write( "D) x=-3, y=-7, z=1
\n" ); document.write( "E) x=-3, y=-6, z=-8
\n" ); document.write( "F) x=38, y=22, z=-26
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\n" ); document.write( "I know that x = -3, and I've tried substituting this into the other two equations, then solving one into the other, but it doesn't match any of the answers! Could I have some help? Thank you for your time! \n" ); document.write( "
Algebra.Com's Answer #471323 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "(1)                 5x = -15\r\n" );
document.write( "(2)     -11x - 4y + 7z = 1\r\n" );
document.write( "(3)        3x - 3y + z = 1 \r\n" );
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document.write( "Solve (1) for x\r\n" );
document.write( "5x = -15\r\n" );
document.write( " x = -3\r\n" );
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document.write( "Substitute x = -3 in (2)\r\n" );
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document.write( "   -11x - 4y + 7z = 1\r\n" );
document.write( "-11(-3) - 4y + 7z = 1\r\n" );
document.write( "     33 - 4y + 7z = 1\r\n" );
document.write( "(4)      -4y + 7z = -32\r\n" );
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document.write( "Substitute x = -3 in (3)\r\n" );
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document.write( "      3x - 3y + z = 1\r\n" );
document.write( "   3(-3) - 3y + z = 1\r\n" );
document.write( "      -9 - 3y + z = 1\r\n" );
document.write( "(5)       -3y + z = 10\r\n" );
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document.write( "So you have this system:\r\n" );
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document.write( "(4)      -4y + 7z = -32\r\n" );
document.write( "(5)      -3y +  z =  10\r\n" );
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document.write( "Solve (5) for z\r\n" );
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document.write( "    -3y + z = 10\r\n" );
document.write( "(6)       z = 10 + 3y\r\n" );
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document.write( "Substitute in (4)\r\n" );
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document.write( "        -4y + 7z = -32\r\n" );
document.write( "-4y + 7(10 + 3y) = -32\r\n" );
document.write( "  -4y + 70 + 21y = -32\r\n" );
document.write( "        17y + 70 = -32\r\n" );
document.write( "             17y = -102\r\n" );
document.write( "               y = -6\r\n" );
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document.write( "Substitute in (6)\r\n" );
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document.write( "(6)       z = 10 + 3(-6)\r\n" );
document.write( "          z = 10 - 18\r\n" );
document.write( "          z = -8\r\n" );
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document.write( "Answer:   E) x=-3, y=-6, z=-8  \r\n" );
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document.write( "Edwin
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