document.write( "Question 963090: Let A=[1 3
\n" ); document.write( " 2 9] , calculate A−1\r
\n" ); document.write( "\n" ); document.write( "What in the world do I do with this?! Please help! \n" ); document.write( "

Algebra.Com's Answer #588421 by Fombitz(32388) $\"\"$ $\"About$

You can put this solution on YOUR website!
To find the inverse of a 2x2 matrix, first find the determinant.
\n" ); document.write( " $\"D=1%289%29-2%283%29=9-6=3\"$
\n" ); document.write( "For a 2x2 matrix,
\n" ); document.write( " $\"A=%28matrix%282%2C2%2Ca%2Cb%2Cc%2Cd%29%29\"$
\n" ); document.write( "the inverse is just,
\n" ); document.write( " $\"A%5E%28-1%29=%281%2FD%29%2A%28matrix%282%2C2%2Cd%2C-b%2C-c%2Ca%29%29\"$
\n" ); document.write( "So in this case,
\n" ); document.write( " $\"A%5E%28-1%29=%281%2F3%29%2A%28matrix%282%2C2%2C9%2C-3%2C-2%2C1%29%29\"$
\n" ); document.write( ".
\n" ); document.write( ".\r
\n" ); document.write( "\n" ); document.write( " $\"A%5E%28-1%29=%28matrix%282%2C2%2C3%2C-1%2C-2%2F3%2C1%2F3%29%29\"$ \n" ); document.write( "

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