document.write( "Question 948208: A parabola whose axis is parallel to the y-axis passes through the points (1,1), (2,2) and (-1,5). Find its equation. \n" ); document.write( "
Algebra.Com's Answer #578711 by MathLover1(20850)\"\" \"About 
You can put this solution on YOUR website!
\"y+=+ax%5E2%2B+bx+%2B+c\"\r
\n" ); document.write( "\n" ); document.write( "use given points to set up the system of equations to find \"a\",\"b\",and \"c\"\r
\n" ); document.write( "\n" ); document.write( "(\"1\", \"1\") ----> \"a+%2B+b+%2B+c+=+1\"
\n" ); document.write( "(\"2\",\"+2\") ----> \"4a+%2B+2b+%2B+c+=+2\"
\n" ); document.write( "(\"-1\",\"5\") ---> \"a+-b+%2B+c+=+5\"\r
\n" ); document.write( "\n" ); document.write( "Solve simultaneous equations:subtract first from second one\r
\n" ); document.write( "\n" ); document.write( "\"4a+%2B+2b+%2B+c+-%28a+%2B+b+%2B+c%29=+2-1\"
\n" ); document.write( "\"4a+%2B+2b+%2B+c+-a+-+b+-+c=+1\"
\n" ); document.write( "\"3a+%2B+b++=+1\"...solve for \"a\"\r
\n" ); document.write( "\n" ); document.write( "=>\"3a+=+1-b\"
\n" ); document.write( "=>\"a+=+1%2F3-b%2F3\".......1a\r
\n" ); document.write( "\n" ); document.write( "add first and third one:
\n" ); document.write( "\"a+%2B+b+%2B+c+%2Ba+-b+%2B+c+=+1%2B5\"
\n" ); document.write( "\"2a+%2B+2c+=+6\" ....solve for \"a\"
\n" ); document.write( "=>\"2a++=+6+-2c\"
\n" ); document.write( "=>\"a++=+3+-c\".........2a\r
\n" ); document.write( "\n" ); document.write( "go to first eq., substitute \"a\" from 1a\r
\n" ); document.write( "\n" ); document.write( "\"1%2F3-b%2F3+%2B+b+%2B+c+=+1\"
\n" ); document.write( "\"2b%2F3+%2B+c+=+1-1%2F3\"
\n" ); document.write( "\"2b%2F3+%2B+c+=+2%2F3\"
\n" ); document.write( "\"2b+%2B+3c+=+2\"
\n" ); document.write( "\"2b+=+2-3c\" ....solve for \"b\"
\n" ); document.write( "\"b+=+1-3c%2F2\"...............1b\r
\n" ); document.write( "\n" ); document.write( "go to eq.2, substitute \"a\" from 2a and \"b\" from 1b\r
\n" ); document.write( "\n" ); document.write( "\"4%28+3+-c%29%2B+2%28+1-3c+%2F2%29%2B+c+=+2\"
\n" ); document.write( "\"12+-4c%2B+2-3c+%2B+c+=+2\"
\n" ); document.write( "\"14-6c+=+2\"
\n" ); document.write( "\"14-2+=+6c\"
\n" ); document.write( "\"12+=+6c\"
\n" ); document.write( "\"highlight%28c=2%29\"\r
\n" ); document.write( "\n" ); document.write( "now find \"a\"
\n" ); document.write( "=>\"a++=+3+-c\"
\n" ); document.write( "=>\"a++=+3+-2\"
\n" ); document.write( "=>\"highlight%28a++=+1%29\"\r
\n" ); document.write( "\n" ); document.write( "and \"b\"
\n" ); document.write( "\"b+=+1-%283%2A2%29%2F2\"
\n" ); document.write( "=>\"b+=+1-3\"
\n" ); document.write( "=>\"highlight%28b+=+-2%29\"\r
\n" ); document.write( "\n" ); document.write( "so, your equation is:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"highlight%28y+=+x%5E2+-2x+%2B+2%29\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( " \r
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );