document.write( "Question 1158969: Hi!
\n" ); document.write( "I have been trying to use old, retired ACT exams to prepare to take the actual test, and in checking my work to find what I need to improve on I've run into a problem that I have solved but don't quite understand. \r
\n" ); document.write( "\n" ); document.write( "\"The solution of the system of equations below is the set of all (x,y)such that 2x-3y=6. What is the value of k?\r
\n" ); document.write( "\n" ); document.write( "18x-27y=54
\n" ); document.write( "6x+ky=-2k\r
\n" ); document.write( "\n" ); document.write( "A.-9
\n" ); document.write( "B.-1
\n" ); document.write( "C.3
\n" ); document.write( "D.6
\n" ); document.write( "E.9\r
\n" ); document.write( "\n" ); document.write( "I solved by substituting each of the options given for k in the bottom equation, and then using the elimination method for solving systems of equations. However, it was very time consuming and I did not understand how the equation in the paragraph fit in with the other two equations. The answer was A. I did not understand why the answer that made the two equations come out to 0 was correct. I did not even use the equation in the paragraph to solve, and I only got the answer correct when fixing my work later, not when taking the test (I simulated an actual test as much as I could by timing myself). Is there a faster, more accurate method? Perhaps using the calculator? I do own a graphing calculator, but it is not a TI-84. \r
\n" ); document.write( "\n" ); document.write( "I hope this makes sense. Thank you for taking the time to help me!\r
\n" ); document.write( "\n" ); document.write( "Anna McLeran
\n" ); document.write( "

Algebra.Com's Answer #781965 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!
\"18x-27y=54\"
\n" ); document.write( "\"6x%2Bky=-2k\".......both sides multiply by \"3\"
\n" ); document.write( "---------------------
\n" ); document.write( "\"18x-27y=54\"
\n" ); document.write( "\"18x%2B3ky=-6k\"
\n" ); document.write( "--------------------------subtract\r
\n" ); document.write( "\n" ); document.write( "\"18x-27y-18x-3ky=54-%28-6k%29\"\r
\n" ); document.write( "\n" ); document.write( "\"-27y-3ky=54%2B6k\"........group\r
\n" ); document.write( "\n" ); document.write( "\"%28-3ky-27y%29=%286k%2B54%29\"...factor out common\r
\n" ); document.write( "\n" ); document.write( "\"-3y%28k+%2B+9%29+=+6%28k+%2B+9%29\"\r
\n" ); document.write( "\n" ); document.write( "\"-3y%28k+%2B+9%29-+6%28k+%2B+9%29=0\"\r
\n" ); document.write( "\n" ); document.write( "\"%28-3y+-+6+%29%28k+%2B+9%29=0\"\r
\n" ); document.write( "\n" ); document.write( "=>
\n" ); document.write( "\"%28k+%2B+9%29=0\" -> \"highlight%28k=-9%29\"\r
\n" ); document.write( "\n" ); document.write( "\"-3y-+6+=0\"=>\"3y=-6\"->\"y=-2\"\r
\n" ); document.write( "\n" ); document.write( "find \"x\"\r
\n" ); document.write( "\n" ); document.write( "\"6x-9%28-2%29=-2%28-9%29\"\r
\n" ); document.write( "\n" ); document.write( "\"6x%2B18=18\"\r
\n" ); document.write( "\n" ); document.write( "\"6x=18-18\"\r
\n" ); document.write( "\n" ); document.write( "\"6x=0\"\r
\n" ); document.write( "\n" ); document.write( "\"x=0\"\r
\n" ); document.write( "\n" ); document.write( "so, check your system:\r
\n" ); document.write( "\n" ); document.write( "\"18x-27y=54\"
\n" ); document.write( "\"18%2A0-27%28-2%29=54\"
\n" ); document.write( "\"54=54\"-> true\r
\n" ); document.write( "\n" ); document.write( "\"6x%2Bky=-2k\"
\n" ); document.write( "\"6%2A0-9%28-2%29=-2%28-9%29\"
\n" ); document.write( "\"18=18\"->true\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );