document.write( "Question 170179: Solve the system of equations using the substitution method. If the answer is a unique solution,present it as an ordered pair (x,y). If not specify whether the answer is \"no solution\" or infintely many solutions.\"
\n" ); document.write( "3x+y=7
\n" ); document.write( "4x-y=21\r
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\n" ); document.write( "\n" ); document.write( "Solve the system of equations using the addition (elimination) method. If the answer is a unique solution, present it as an ordered pair: (x,y). If not specify whether the answer is \"no solution\" or infintely many solutions.\r
\n" ); document.write( "\n" ); document.write( "6x+2y=2
\n" ); document.write( "3x+5y=5\r
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\n" ); document.write( "\n" ); document.write( "Solve the system of equations using the addition (elimination) method. If the answer is a unique solution, present it as an ordered pair:(x,y). If not, specify whether the answer is no solution or \"infinitely many solutions.\"\r
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\n" ); document.write( "-12x+9y=5
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Algebra.Com's Answer #125621 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
I'll do the first two to get you started\r
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\n" ); document.write( "\n" ); document.write( "Start with the given system of equations:\r
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\n" ); document.write( "\n" ); document.write( "\"system%283x%2By=7%2C4x-y=21%29\"\r
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\n" ); document.write( "\n" ); document.write( "Now in order to solve this system by using substitution, we need to solve (or isolate) one variable. I'm going to solve for y.\r
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\n" ); document.write( "\n" ); document.write( "So let's isolate y in the first equation\r
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\n" ); document.write( "\n" ); document.write( "\"3x%2By=7\" Start with the first equation\r
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\n" ); document.write( "\n" ); document.write( "\"y=7-3x\" Subtract \"3x\" from both sides\r
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\n" ); document.write( "\n" ); document.write( "\"y=-3x%2B7\" Rearrange the equation\r
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\n" ); document.write( "\n" ); document.write( "Since \"y=-3x%2B7\", we can now replace each \"y\" in the second equation with \"-3x%2B7\" to solve for \"x\"\r
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\n" ); document.write( "\n" ); document.write( "\"4x-highlight%28%28-3x%2B7%29%29=21\" Plug in \"y=-3x%2B7\" into the second equation. In other words, replace each \"y\" with \"-3x%2B7\". Notice we've eliminated the \"y\" variables. So we now have a simple equation with one unknown.\r
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\n" ); document.write( "\n" ); document.write( "\"4x%2B3x-7=21\" Distribute the negative\r
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\n" ); document.write( "\n" ); document.write( "\"7x-7=21\" Combine like terms on the left side\r
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\n" ); document.write( "\n" ); document.write( "\"7x=21%2B7\"Add 7 to both sides\r
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\n" ); document.write( "\n" ); document.write( "\"7x=28\" Combine like terms on the right side\r
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\n" ); document.write( "\n" ); document.write( "\"x=%2828%29%2F%287%29\" Divide both sides by 7 to isolate x\r
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\n" ); document.write( "\n" ); document.write( "\"x=4\" Divide\r
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\n" ); document.write( "\n" ); document.write( "-----------------First Answer------------------------------\r
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\n" ); document.write( "\n" ); document.write( "So the first part of our answer is: \"x=4\"\r
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\n" ); document.write( "\n" ); document.write( "Since we know that \"x=4\" we can plug it into the equation \"y=-3x%2B7\" (remember we previously solved for \"y\" in the first equation).\r
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\n" ); document.write( "\n" ); document.write( "\"y=-3x%2B7\" Start with the equation where \"y\" was previously isolated.\r
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\n" ); document.write( "\n" ); document.write( "\"y=-3%284%29%2B7\" Plug in \"x=4\"\r
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\n" ); document.write( "\n" ); document.write( "\"y=-12%2B7\" Multiply\r
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\n" ); document.write( "\n" ); document.write( "\"y=-5\" Combine like terms \r
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\n" ); document.write( "\n" ); document.write( "-----------------Second Answer------------------------------\r
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\n" ); document.write( "\n" ); document.write( "So the second part of our answer is: \"y=-5\"\r
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\n" ); document.write( "\n" ); document.write( "-----------------Summary------------------------------\r
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\n" ); document.write( "\n" ); document.write( "So our answers are:\r
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\n" ); document.write( "\n" ); document.write( "\"x=4\" and \"y=-5\"\r
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\n" ); document.write( "\n" ); document.write( "which form the point \r
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\n" ); document.write( "\n" ); document.write( "Now let's graph the two equations (if you need help with graphing, check out this solver)\r
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\n" ); document.write( "\n" ); document.write( "From the graph, we can see that the two equations intersect at . This visually verifies our answer.\r
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\n" ); document.write( "\n" ); document.write( " graph of \"3x%2By=7\" (red) and \"4x-y=21\" (green) and the intersection of the lines (blue circle).\r
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\n" ); document.write( "\n" ); document.write( "# 2\r
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\n" ); document.write( "\n" ); document.write( "Start with the given system of equations:\r
\n" ); document.write( "\n" ); document.write( "\"system%286x%2B2y=2%2C3x%2B5y=5%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"-2%283x%2B5y%29=-2%285%29\" Multiply the both sides of the second equation by -2.\r
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\n" ); document.write( "\n" ); document.write( "\"-6x-10y=-10\" Distribute and multiply.\r
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\n" ); document.write( "\n" ); document.write( "So we have the new system of equations:\r
\n" ); document.write( "\n" ); document.write( "\"system%286x%2B2y=2%2C-6x-10y=-10%29\"\r
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\n" ); document.write( "\n" ); document.write( "Now add the equations together. You can do this by simply adding the two left sides and the two right sides separately like this:\r
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\n" ); document.write( "\n" ); document.write( "\"%286x%2B2y%29%2B%28-6x-10y%29=%282%29%2B%28-10%29\"\r
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\n" ); document.write( "\n" ); document.write( "\"%286x%2B-6x%29%2B%282y%2B-10y%29=2%2B-10\" Group like terms.\r
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\n" ); document.write( "\n" ); document.write( "\"0x%2B-8y=-8\" Combine like terms. Notice how the x terms cancel out.\r
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\n" ); document.write( "\n" ); document.write( "\"-8y=-8\" Simplify.\r
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\n" ); document.write( "\n" ); document.write( "\"y=%28-8%29%2F%28-8%29\" Divide both sides by \"-8\" to isolate \"y\".\r
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\n" ); document.write( "\n" ); document.write( "\"y=1\" Reduce.\r
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\n" ); document.write( "\n" ); document.write( "\"6x%2B2y=2\" Now go back to the first equation.\r
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\n" ); document.write( "\n" ); document.write( "\"6x%2B2%281%29=2\" Plug in \"y=1\".\r
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\n" ); document.write( "\n" ); document.write( "\"6x%2B2=2\" Multiply.\r
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\n" ); document.write( "\n" ); document.write( "\"6x=2-2\" Subtract \"2\" from both sides.\r
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\n" ); document.write( "\n" ); document.write( "\"6x=0\" Combine like terms on the right side.\r
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\n" ); document.write( "\n" ); document.write( "\"x=%280%29%2F%286%29\" Divide both sides by \"6\" to isolate \"x\".\r
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\n" ); document.write( "\n" ); document.write( "\"x=0\" Reduce.\r
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\n" ); document.write( "\n" ); document.write( "So our answer is \"x=0\" and \"y=1\".\r
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\n" ); document.write( "\n" ); document.write( "Which form the ordered pair .\r
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\n" ); document.write( "\n" ); document.write( "This means that the system is consistent and independent.\r
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\n" ); document.write( "\n" ); document.write( "Notice when we graph the equations, we see that they intersect at . So this visually verifies our answer.\r
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\n" ); document.write( "\n" ); document.write( " Graph of \"6x%2B2y=2\" (red) and \"3x%2B5y=5\" (green) \r
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