document.write( "Question 213455: what is the vertex of parabola y=8x+1-4x^2? I need all the steps so I can understand the solution.\r
\n" ); document.write( "\n" ); document.write( "Thank you \n" ); document.write( "
Algebra.Com's Answer #161237 by nerdybill(7384)\"\" \"About 
You can put this solution on YOUR website!
Rewrite:
\n" ); document.write( "y=8x+1-4x^2
\n" ); document.write( "as:
\n" ); document.write( "y = -4x^2+8x+1
\n" ); document.write( ".
\n" ); document.write( "There are two ways to do it. By \"completing the square\" OR by find the \"axis of symmetry\".
\n" ); document.write( ".
\n" ); document.write( "I'll do the latter. The \"axis of symmetry\" defines a line which divides the parabola right down the middle. Once you know that, you can determine the vertex.
\n" ); document.write( ".
\n" ); document.write( "\"axis of symmetry\" is found by plugging in the values to:
\n" ); document.write( "-b/(2a) (derives from a portion of the quadratic equation)
\n" ); document.write( "-8/(2*(-4))
\n" ); document.write( "-8/-8
\n" ); document.write( "-1
\n" ); document.write( "Our axis of symmetry is then at:
\n" ); document.write( "x = -1
\n" ); document.write( ".
\n" ); document.write( "We now have half of our vertex: (-1, __)
\n" ); document.write( "to find the y coordinate, subsititute -1 for 'x' into the equation and solve for y:
\n" ); document.write( "y = -4x^2+8x+1
\n" ); document.write( "y = -4(1)^2+8(1)+1
\n" ); document.write( "y = -4+8+1
\n" ); document.write( "y = 5
\n" ); document.write( ".
\n" ); document.write( "Solution:
\n" ); document.write( "Vertex is at (-1, 5)\r
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