document.write( "Question 1000503: Solving linear equations by addition \r
\n" ); document.write( "\n" ); document.write( "I have tried adding three to both sides of the first equation on this question but I'm still not coming out with the right answer \r
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Algebra.Com's Answer #642757 by Edwin McCravy(20060) $\"\"$ $\"About$

You can put this solution on YOUR website!

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document.write( "Get them so that the terms with s's and t's\r\n" );
document.write( "are on the left side, and the terms without \r\n" );
document.write( "them are on the right side.\r\n" );
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document.write( "The first equation is already like that.\r\n" );
document.write( "Get the second one that way by adding -2t to\r\n" );
document.write( "both sides:\r\n" );
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document.write( "     5s = 2t+7\r\n" );
document.write( "  5s-2t = 7\r\n" );
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document.write( "Now let's make the t's cancel out.\r\n" );
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document.write( "the coefficient of t in the 1st equation is +3\r\n" );
document.write( "the coefficient of t in the 2nd equation is -2\r\n" );
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document.write( "We want to change the +3 and the -2 so they will\r\n" );
document.write( "cancel.\r\n" );
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document.write( "They already have opposite signs.\r\n" );
document.write( "The least common multiple of 3 and 2 is 6.\r\n" );
document.write( "If we multiply the 1st equation by 2, the coefficient\r\n" );
document.write( "of t will change from +3 to +6\r\n" );
document.write( "If we multiply the 2nd equation by 3, the coefficient\r\n" );
document.write( "of t will change from -2 to -6\r\n" );
document.write( "And then +6 and -6 will cancel.\r\n" );
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document.write( "So let's multiply the 1st equation through by 2,\r\n" );
document.write( "and the 2nd equation through by 3\r\n" );
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document.write( "Now we add the two equations term by term:\r\n" );
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document.write( "4s+15s=19s, +6t-6t=0, and -2+21=19, \r\n" );
document.write( "so we have\r\n" );
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document.write( "Divide both sides by 19, and get\r\n" );
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document.write( "Substitute s=1 into the first original equation:\r\n" );
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document.write( "Add -2 to both sides\r\n" );
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document.write( "Divide both sides by 3\r\n" );
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document.write( "Solution: (s,t) = (1,-1)\r\n" );
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document.write( "Edwin

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