document.write( "Question 940173: -4x-y=-21
\n" ); document.write( "x-2y=12
\n" ); document.write( "Solve by substitution \n" ); document.write( "

Algebra.Com's Answer #572981 by MathLover1(20850) $\"\"$ $\"About$

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\n" ); document.write( " $\"-4x-y=-21\"$ ....eq.1
\n" ); document.write( " $\"x-2y=12+\"$ .....eq.2
\n" ); document.write( "---------------------
\n" ); document.write( "Solve by substitution\r
\n" ); document.write( "\n" ); document.write( " $\"x-2y=12+\"$ .....eq.2...solve for $\"x\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"x=2y%2B12+\"$ ...substitute in eq.1\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " $\"-4%282y%2B12%29-y=-21\"$ ....eq.1...solve for $\"y\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"-8y-48-y=-21\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"-9y-48=-21\"$ ...both sides multiply by $\"-1\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"9y%2B48=21\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"9y=21-48\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"9y=-27\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"y=-27%2F9\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"highlight%28y=-3%29\"$ \r
\n" ); document.write( "\n" ); document.write( "go to\r
\n" ); document.write( "\n" ); document.write( " $\"x=2y%2B12+\"$ ...substitute $\"-3\"$ for $\"y\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"x=2%28-3%29%2B12+\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"x=-6%2B12+\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"highlight%28x=6%29+\"$ \r
\n" ); document.write( "\n" ); document.write( "so, intersection point of these two lines is: ( $\"6\"$ , $\"-3\"$ )\r
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\n" ); document.write( "\n" ); document.write( "check it on a graph:\r
\n" ); document.write( "\n" ); document.write( "

\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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