document.write( "Question 831410: i got this matrix :
\n" ); document.write( " 3 0 0 -1
\n" ); document.write( " 0 2 -2 1
\n" ); document.write( "-3 3 -2 2
\n" ); document.write( " 6 1 0 1\r
\n" ); document.write( "\n" ); document.write( "i want to find the determinant, i got this :
\n" ); document.write( " |2 -2 1| | 0 2 -2|
\n" ); document.write( "3 |3 -2 2|- 0 + 0 + |-3 3 -2|
\n" ); document.write( " |1 0 1| | 6 1 0|\r
\n" ); document.write( "\n" ); document.write( "and got 3((2x-2)+(2x1)+2)+(42+42) = 84 ?
\n" ); document.write( "where do i got wrong ? \n" ); document.write( "
Algebra.Com's Answer #501339 by AnlytcPhil(1807)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "Don't listen to him.  You can't stop and go \"PDF-ing\" everytime you need \r\n" );
document.write( "to do a small problem.  \r\n" );
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document.write( "First get a 0 in the upper left corner by multiplying the 4th column by 3\r\n" );
document.write( "and adding it to the first column.  \r\n" );
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document.write( "| 3  0  0 -1|               | 0  0  0 -1|         | 3  2 -2|    | 3  2 -2|\r\n" );
document.write( "| 0  2 -2  1|  3C4+C1->C1   | 3  2 -2  1|  = -(-1)| 3  3 -2| =  | 3  3 -2|\r\n" );
document.write( "|-3  3 -2  2|               | 3  3 -2  2|         | 9  1  0|    | 9  1  0|\r\n" );
document.write( "| 6  1  0  1|               | 9  1  0  1|\r\n" );
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document.write( "When you get down to a 3×3 determinant, it's often too tedious to\r\n" );
document.write( "always expand it by minors.  I'm sure your error was a sign or \r\n" );
document.write( "something.  Expand by minors until you get down to a 3×3, then\r\n" );
document.write( "do the 3×3 this following way.  You're less likely to make a mistake.\r\n" );
document.write( "Copy the first two columns over to the right of the determinant\r\n" );
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document.write( "| 3  2 -2| 3  2\r\n" );
document.write( "| 3  3 -2| 3  3\r\n" );
document.write( "| 9  1  0| 9  1\r\n" );
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document.write( "Then multiply the three diagonals that slant this way \ and add them:\r\n" );
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document.write( "(3)(3)(0) + (2)(-2)(9) + (-2)(3)(1) = 0-36-6 = -42\r\n" );
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document.write( "Then multiply the three diagonals that slant this way / and add them\r\n" );
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document.write( "(-2)(3)(9) + (3)(-2)(1) + (-2)(3)(0) = -54 - 6 - 0 = -60\r\n" );
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document.write( "Then subtract (-42)-(-60) = -42 + 60 = 18\r\n" );
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document.write( "Edwin
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