document.write( "Question 120219: Solve for x: 3x^2+5x-7=x^2+8x+28 \n" ); document.write( "
Algebra.Com's Answer #88101 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!

\n" ); document.write( "\"3x%5E2%2B5x-7=x%5E2%2B8x%2B28\" Start with the given equation\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"3x%5E2%2B5x-7-x%5E2-8x-28=0\" Subtract x^2 from both sides. Subtract 8x from both sides. Subtract 28 from both sides. \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"2x%5E2-3x-35=0\" Combine like terms\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Let's use the quadratic formula to solve for x:\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Starting with the general quadratic\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"ax%5E2%2Bbx%2Bc=0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "the general solution using the quadratic equation is:\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( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So lets solve \"2%2Ax%5E2-3%2Ax-35=0\" ( notice \"a=2\", \"b=-3\", and \"c=-35\")\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28--3+%2B-+sqrt%28+%28-3%29%5E2-4%2A2%2A-35+%29%29%2F%282%2A2%29\" Plug in a=2, b=-3, and c=-35\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%283+%2B-+sqrt%28+%28-3%29%5E2-4%2A2%2A-35+%29%29%2F%282%2A2%29\" Negate -3 to get 3\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%283+%2B-+sqrt%28+9-4%2A2%2A-35+%29%29%2F%282%2A2%29\" Square -3 to get 9 (note: remember when you square -3, you must square the negative as well. This is because \"%28-3%29%5E2=-3%2A-3=9\".)\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%283+%2B-+sqrt%28+9%2B280+%29%29%2F%282%2A2%29\" Multiply \"-4%2A-35%2A2\" to get \"280\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%283+%2B-+sqrt%28+289+%29%29%2F%282%2A2%29\" Combine like terms in the radicand (everything under the square root)\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%283+%2B-+17%29%2F%282%2A2%29\" Simplify the square root (note: If you need help with simplifying the square root, check out this solver)\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%283+%2B-+17%29%2F4\" Multiply 2 and 2 to get 4\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So now the expression breaks down into two parts\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%283+%2B+17%29%2F4\" or \"x+=+%283+-+17%29%2F4\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Lets look at the first part:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=%283+%2B+17%29%2F4\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=20%2F4\" Add the terms in the numerator\r
\n" ); document.write( "\n" ); document.write( "\"x=5\" Divide\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So one answer is\r
\n" ); document.write( "\n" ); document.write( "\"x=5\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now lets look at the second part:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=%283+-+17%29%2F4\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=-14%2F4\" Subtract the terms in the numerator\r
\n" ); document.write( "\n" ); document.write( "\"x=-7%2F2\" Divide\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So another answer is\r
\n" ); document.write( "\n" ); document.write( "\"x=-7%2F2\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So our solutions are:\r
\n" ); document.write( "\n" ); document.write( "\"x=5\" or \"x=-7%2F2\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );