document.write( "Question 189666: I am having problems finding the vertex of this problem.. could someone please help. \r
\n" ); document.write( "\n" ); document.write( " Problem : Consider the Quadratic function f(x)=4x^2-64. Its vertex is ( ? , ?) Its x-intercepts are x= (?,?) Its y- intercept is y= ?\r
\n" ); document.write( "\n" ); document.write( "How do you find the vertex from an equation like this, I know the formula f(x) = (x-h)^2+k plays a part but I am not sure how it relates to the equation.
\n" ); document.write( "

Algebra.Com's Answer #142309 by jim_thompson5910(35256)\"\" \"About 
You can put this solution on YOUR website!

Vertex:

\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "In order to find the vertex, we first need to find the x-coordinate of the vertex.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "To find the x-coordinate of the vertex, use this formula: \"x=%28-b%29%2F%282a%29\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=%28-b%29%2F%282a%29\" Start with the given formula.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "From \"y=4x%5E2-64\", we can see that \"a=4\", \"b=0\", and \"c=-64\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=%28-%280%29%29%2F%282%284%29%29\" Plug in \"a=4\" and \"b=0\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=%280%29%2F%288%29\" Multiply 2 and \"4\" to get \"8\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x=0\" Divide.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So the x-coordinate of the vertex is \"x=0\". Note: this means that the axis of symmetry is also \"x=0\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Now that we know the x-coordinate of the vertex, we can use it to find the y-coordinate of the vertex.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=4x%5E2-64\" Start with the given equation.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=4%280%29%5E2-64\" Plug in \"x=0\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=4%280%29-64\" Square \"0\" to get \"0\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=0-64\" Multiply \"4\" and \"0\" to get \"0\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=-64\" Combine like terms.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So the y-coordinate of the vertex is \"y=-64\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So the vertex is .\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\r
\n" ); document.write( "\n" ); document.write( "

X-Intercept(s):

\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Remember, the x-intercepts occur when \"y=0\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=4x%5E2-64\" Start with the given equation.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"0=4x%5E2-64\" Plug in \"y=0\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Notice we have a quadratic equation in the form of \"ax%5E2%2Bbx%2Bc\" where \"a=4\", \"b=0\", and \"c=-64\"\r
\n" ); document.write( "
\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( "\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4ac+%29%29%2F%282a%29\" Start with the quadratic formula\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%28-%280%29+%2B-+sqrt%28+%280%29%5E2-4%284%29%28-64%29+%29%29%2F%282%284%29%29\" Plug in \"a=4\", \"b=0\", and \"c=-64\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%280+%2B-+sqrt%28+0-4%284%29%28-64%29+%29%29%2F%282%284%29%29\" Square \"0\" to get \"0\". \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%280+%2B-+sqrt%28+0--1024+%29%29%2F%282%284%29%29\" Multiply \"4%284%29%28-64%29\" to get \"-1024\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%280+%2B-+sqrt%28+0%2B1024+%29%29%2F%282%284%29%29\" Rewrite \"sqrt%280--1024%29\" as \"sqrt%280%2B1024%29\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%280+%2B-+sqrt%28+1024+%29%29%2F%282%284%29%29\" Add \"0\" to \"1024\" to get \"1024\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%280+%2B-+sqrt%28+1024+%29%29%2F%288%29\" Multiply \"2\" and \"4\" to get \"8\". \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%280+%2B-+32%29%2F%288%29\" Take the square root of \"1024\" to get \"32\". \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%280+%2B+32%29%2F%288%29\" or \"x+=+%280+-+32%29%2F%288%29\" Break up the expression. \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+%2832%29%2F%288%29\" or \"x+=++%28-32%29%2F%288%29\" Combine like terms. \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"x+=+4\" or \"x+=+-4\" Simplify. \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So the answers are \"x+=+4\" or \"x+=+-4\" \r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "This means that the x-intercepts are (4,0) and (-4,0)\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "

Y-Intercept:

\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Remember, the y-intercept occurs when \"x=0\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=4x%5E2-64\" Start with the given equation.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=4%280%29%5E2-64\" Plug in \"x=0\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=4%280%29-64\" Square \"0\" to get \"0\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=0-64\" Multiply \"4\" and \"0\" to get \"0\".\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"y=-64\" Combine like terms.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "So the y-intercept is (0,-64)
\n" ); document.write( "
\n" );