document.write( "Question 982691: Find the value of k that makes the sum of the roots of 3x^2+18=(3k+2)x equal to 6 \n" ); document.write( "
Algebra.Com's Answer #603547 by MathLover1(20849)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "the sum of the roots are equal to \"-b%2Fa\"
\n" ); document.write( "the product of the roots are equal to \"c%2Fa\"
\n" ); document.write( "the standard form of the quadratic equation is\r
\n" ); document.write( "\n" ); document.write( "\"+ax%5E2+%2B+bx+%2B+c+=+0\"\r
\n" ); document.write( "\n" ); document.write( "your equation is:\r
\n" ); document.write( "\n" ); document.write( "\"3x%5E2+%2B+18+=+%283k%2B2%29x\"\r
\n" ); document.write( "\n" ); document.write( "subtract \"%283k%2B2%29x\" from both sides of the equation to get:\r
\n" ); document.write( "\n" ); document.write( "\"3x%5E2+-+%283k%2B2%29x+%2B+18+=+0\"\r
\n" ); document.write( "\n" ); document.write( "this equation is now in standard form of \"ax%5E2+%2B+bx+%2B+c=0\" where:
\n" ); document.write( "\"a+=+3\"
\n" ); document.write( "\"b+=+-%283k%2B2%29\"
\n" ); document.write( "\"c+=+18\"\r
\n" ); document.write( "\n" ); document.write( "sum of the roots are \"-b%2Fa\" which becomes \"%283k%2B2%29%2F3\" \r
\n" ); document.write( "\n" ); document.write( "since sum of the roots is equal to \"6\", this means that \"%283k%2B2%29%2F3+=+6\"\r
\n" ); document.write( "\n" ); document.write( "solve for \"k\"\r
\n" ); document.write( "\n" ); document.write( "multiply both sides of this equation by \"3\" to get:\r
\n" ); document.write( "\n" ); document.write( "\"3k%2B2+=+18\"\r
\n" ); document.write( "\n" ); document.write( "subtract \"2\" from both sides of this equation to get:\r
\n" ); document.write( "\n" ); document.write( "\"3k+=+16\"\r
\n" ); document.write( "\n" ); document.write( "divide both sides of this equation by \"3\" to get:\r
\n" ); document.write( "\n" ); document.write( "\"k+=+16%2F3\"\r
\n" ); document.write( "\n" ); document.write( "that should be the value of \"+k\"\r
\n" ); document.write( "\n" ); document.write( "check if that works:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "when \"k+=+16%2F3\", \"3k%2B2+=+3%2A16%2F3+%2B+2+=+18\"\r
\n" ); document.write( "\n" ); document.write( "then your equation \"3x%5E2+%2B+18+=+%283k%2B2%29x\" becomes:\r
\n" ); document.write( "\n" ); document.write( "\"3x%5E2+%2B+18+=+18x\"\r
\n" ); document.write( "\n" ); document.write( "subtract \"18x\" from both sides of this equation to get:\r
\n" ); document.write( "\n" ); document.write( "\"3x%5E2+-+18x+%2B+18+=+0\"\r
\n" ); document.write( "\n" ); document.write( "divide both sides of this equation by \"3+\"to get:\r
\n" ); document.write( "\n" ); document.write( "\"x%5E2+-+6x+%2B+6+=+0\"\r
\n" ); document.write( "\n" ); document.write( "we can use the formula of sum of the roots =>\"+-b%2Fa\" to get \"6%2F1+=+6\"\r
\n" ); document.write( "\n" ); document.write( "let's find the roots to see if the formula gave us the right answer.\r
\n" ); document.write( "\n" ); document.write( "the roots of this equation are:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\" \r
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-%28-6%29+%2B-+sqrt%28+%28-6%29%5E2-4%2A1%2A6+%29%29%2F%282%2A1%29+\" \r
\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+sqrt%28+36-24+%29%29%2F2+\"\r
\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+sqrt%28+12+%29%29%2F2+\" \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%286+%2B-+sqrt%28+4%2A3%29%29%2F2+\" \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28cross%286%293+%2B-+cross%282%29sqrt%28+3+%29%29%2Fcross%282%29+\" \r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%283+%2B-+sqrt%28+3+%29%29+\" \r
\n" ); document.write( "\n" ); document.write( "roots: \r
\n" ); document.write( "\n" ); document.write( "\"x+=+3+%2B+sqrt%28+3+%29+\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+3+-sqrt%28+3+%29+\"\r
\n" ); document.write( "\n" ); document.write( "and the sum is \"+%28+3+%2B+sqrt%28+3+%29%29%2B%283+-sqrt%28+3+%29%29=3%2Bsqrt%28+3+%29%2B3-sqrt%28+3+%29=6+\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );