document.write( "Question 976194: I'm having trouble understanding how to write equations that relate x and y. For example, what equation am I supposed to write if x=4 and y=12. would it be 3x=y? \n" ); document.write( "

Algebra.Com's Answer #597831 by MathLover1(20850) $\"\"$ $\"About$

You can put this solution on YOUR website!
we have:
\n" ); document.write( "Direct Variation
\n" ); document.write( "When two variables, $\"x\"$ and $\"y\"$ vary $\"directly\"$ , then
\n" ); document.write( " $\"y+=+kx\"$ where $\"k\"$ is a constant called the \"constant of proportionality.\"
\n" ); document.write( "When there is $\"direct\"$ variation between variables $\"x\"$ and $\"y\"$ , $\"doubling\"$ the value of $\"x\"$ will $\"always\"$ result in $\"y\"$ being $\"doubled\"$ . Also, if $\"x\"$ is cut in half, then $\"y\"$ is cut in half. \r
\n" ); document.write( "\n" ); document.write( "Inverse variation
\n" ); document.write( "When two variables, $\"x\"$ and $\"y\"$ vary $\"inversely\"$ , then
\n" ); document.write( " $\"y+=+k%281%2Fx%29+\"$
\n" ); document.write( "or
\n" ); document.write( " $\"y+=+k%2Fx\"$
\n" ); document.write( "or
\n" ); document.write( " $\"xy+=+k\"$
\n" ); document.write( "where $\"k\"$ is a constant called the \"constant of proportionality.\" When there is $\"inverse\"$ variation between variables $\"x\"$ and $\"y\"$ , $\"doubling\"$ the value of $\"x\"$ will $\"always\"$ result in $\"y\"$ being
\n" ); document.write( " $\"cut\"$ in $\"half\"$ . Also, if $\"x\"$ is cut in half, then $\"y\"$ is doubled. \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "in your example, if $\"x=4\"$ and $\"y=12\"$ then $\"y=kx\"$ => $\"12=k%2A4\"$ => $\"k=12%2F4\"$ => $\"k=3\"$ =>if $\"x=4\"$ and $\"y=12\"$ then the constant of proportionality is $\"3\"$ \r
\n" ); document.write( "\n" ); document.write( "so, yes, it would be $\"y=3x\"$ \r
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