document.write( "Question 1074024: The variable x varies jointly with y and z use the given vales to write an
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Algebra.Com's Answer #689416 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
The variable x varies jointly with y and z use the given vales to write an equation relating x,y and z. x=2 when y=3 and z=-4, then find y when x=8 and z =1
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document.write( "For all such problems, start with this:\r\n" );
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document.write( "Varying           \"directly\" or product of \"jointlys\" or 1 if none \r\n" );
document.write( "quantity  = k * ----------------------------------------------------------\r\n" );
document.write( "                inversely variable or product of \"inverselys\" or 1 if none\r\n" );
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document.write( "In this problem the varying quantity is x.\r\n" );
document.write( "there are no \"directly\"s or \"inverselys\", so we have\r\n" );
document.write( "the product of the jointlys on top and 1 on the bottom:\r\n" );
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document.write( "\"x=k%2A%28yz%2F1%29\"\r\n" );
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document.write( "\"x=k%2Ayz\"\r\n" );
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document.write( ">>...x = 2 when y = 3 and z = -4...<<\r\n" );
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document.write( "Substitute these values and solve for k:\r\n" );
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document.write( "\"x=k%2Ayz\"\r\n" );
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document.write( "\"%282%29=k%2A%283%29%28-4%29\"\r\n" );
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document.write( "\"2=k%2A%28-12%29\"\r\n" );
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document.write( "\"2%2F-12=k\"\r\n" );
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document.write( "\"-1%2F6=k\"\r\n" );
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document.write( "Next substitute -1/6 for k in\r\n" );
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document.write( "\"x=k%2Ayz\"\r\n" );
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document.write( "\"x=expr%28-1%2F6%29%2Ayz\"\r\n" );
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document.write( "That is the complete equation of variation,\r\n" );
document.write( "which can be used to find any one of the three\r\n" );
document.write( "variables when two of them are given\r\n" );
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document.write( ">>...find y when x=8 and z=1 <<\r\n" );
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document.write( "Now we substitute those values into\r\n" );
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document.write( "\"x=expr%28-1%2F6%29%2Ayz\"\r\n" );
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document.write( "and solve for y.\r\n" );
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document.write( "I'll let you do that.  If you have trouble, you\r\n" );
document.write( "can tell me in the thank-you note form below,\r\n" );
document.write( "and I'll get back to you by email.  No charge, \r\n" );
document.write( "as I do this for fun.  :)\r\n" );
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document.write( "Edwin

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