document.write( "Question 120129: 2x+3y=24
\n" ); document.write( "y+7x=46\r
\n" ); document.write( "\n" ); document.write( "I have to solve this problem using elimination and I don't understand could someone please help me?
\n" ); document.write( "

Algebra.Com's Answer #88038 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
Solved by pluggable solver: Solving a System of Linear Equations by Elimination/Addition

\n" ); document.write( "
\n" ); document.write( " Lets start with the given system of linear equations
\n" ); document.write( "
\n" ); document.write( " \"2%2Ax%2B3%2Ay=24\"
\n" ); document.write( " \"7%2Ax%2B1%2Ay=46\"
\n" ); document.write( "
\n" ); document.write( " In order to solve for one variable, we must eliminate the other variable. So if we wanted to solve for y, we would have to eliminate x (or vice versa).
\n" ); document.write( "
\n" ); document.write( " So lets eliminate x. In order to do that, we need to have both x coefficients that are equal but have opposite signs (for instance 2 and -2 are equal but have opposite signs). This way they will add to zero.
\n" ); document.write( "
\n" ); document.write( " So to make the x coefficients equal but opposite, we need to multiply both x coefficients by some number to get them to an equal number. So if we wanted to get 2 and 7 to some equal number, we could try to get them to the LCM.
\n" ); document.write( "
\n" ); document.write( " Since the LCM of 2 and 7 is 14, we need to multiply both sides of the top equation by 7 and multiply both sides of the bottom equation by -2 like this:
\n" ); document.write( "
\n" ); document.write( " \"7%2A%282%2Ax%2B3%2Ay%29=%2824%29%2A7\" Multiply the top equation (both sides) by 7
\n" ); document.write( " \"-2%2A%287%2Ax%2B1%2Ay%29=%2846%29%2A-2\" Multiply the bottom equation (both sides) by -2
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So after multiplying we get this:
\n" ); document.write( " \"14%2Ax%2B21%2Ay=168\"
\n" ); document.write( " \"-14%2Ax-2%2Ay=-92\"
\n" ); document.write( "
\n" ); document.write( " Notice how 14 and -14 add to zero (ie \"14%2B-14=0\")
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Now add the equations together. In order to add 2 equations, group like terms and combine them
\n" ); document.write( " \"%2814%2Ax-14%2Ax%29%2B%2821%2Ay-2%2Ay%29=168-92\"
\n" ); document.write( "
\n" ); document.write( " \"%2814-14%29%2Ax%2B%2821-2%29y=168-92\"
\n" ); document.write( "
\n" ); document.write( " \"cross%2814%2B-14%29%2Ax%2B%2821-2%29%2Ay=168-92\" Notice the x coefficients add to zero and cancel out. This means we've eliminated x altogether.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So after adding and canceling out the x terms we're left with:
\n" ); document.write( "
\n" ); document.write( " \"19%2Ay=76\"
\n" ); document.write( "
\n" ); document.write( " \"y=76%2F19\" Divide both sides by \"19\" to solve for y
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"y=4\" Reduce
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " Now plug this answer into the top equation \"2%2Ax%2B3%2Ay=24\" to solve for x
\n" ); document.write( "
\n" ); document.write( " \"2%2Ax%2B3%284%29=24\" Plug in \"y=4\"
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"2%2Ax%2B12=24\" Multiply
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"2%2Ax=24-12\" Subtract \"12\" from both sides
\n" ); document.write( "
\n" ); document.write( " \"2%2Ax=12\" Combine the terms on the right side
\n" ); document.write( "
\n" ); document.write( " \"cross%28%281%2F2%29%282%29%29%2Ax=%2812%29%281%2F2%29\" Multiply both sides by \"1%2F2\". This will cancel out \"2\" on the left side.
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " \"x=6\" Multiply the terms on the right side
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " So our answer is
\n" ); document.write( "
\n" ); document.write( " \"x=6\", \"y=4\"
\n" ); document.write( "
\n" ); document.write( " which also looks like
\n" ); document.write( "
\n" ); document.write( " (\"6\", \"4\")
\n" ); document.write( "
\n" ); document.write( " Notice if we graph the equations (if you need help with graphing, check out this solver)
\n" ); document.write( "
\n" ); document.write( " \"2%2Ax%2B3%2Ay=24\"
\n" ); document.write( " \"7%2Ax%2B1%2Ay=46\"
\n" ); document.write( "
\n" ); document.write( " we get
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " graph of \"2%2Ax%2B3%2Ay=24\" (red) \"7%2Ax%2B1%2Ay=46\" (green) (hint: you may have to solve for y to graph these) and the intersection of the lines (blue circle).
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( " and we can see that the two equations intersect at (\"6\",\"4\"). This verifies our answer.
\n" ); document.write( "
\n" ); document.write( "
\n" );