document.write( "Question 83166: 1) write an equation for the parabola whose vertex is at (-8,4) and passes through (-6,-2)\r
\n" ); document.write( "\n" ); document.write( "2) i need to write: y=x square + 4x - 1 in vertex form\r
\n" ); document.write( "\n" ); document.write( "3) which quadratic function has its vertex at (-2,7) and opens down?
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\n" ); document.write( " thank you \n" ); document.write( "
Algebra.Com's Answer #59684 by Mona27(45)\"\" \"About 
You can put this solution on YOUR website!
The general expression for a quadratic in completed square form is:
\n" ); document.write( "\"y=a%28x%2Bb%29%5E2%2Bc\"
\n" ); document.write( "where the vertex would be (-b,c).
\n" ); document.write( "1) Since the vertex is (-8,4), then the formula should be:
\n" ); document.write( "\"y=a%28x%2B8%29%5E2%2B4\"
\n" ); document.write( "And to find the value of a, substitute the other point (-6,-2) in the equation:
\n" ); document.write( "\"-2=4a%2B4\"
\n" ); document.write( "giving the value of a as \"-3%2F2=-1.5\"\r
\n" ); document.write( "\n" ); document.write( "2) To change a normal quadratic into the completed square form, first take half the coefficient of x (2) and place it in a bracket like this:
\n" ); document.write( "\"%28x%2B2%29%5E2\"
\n" ); document.write( "Now this expression gives you \"x%5E2%2B4x%2B4\" and since we only need the first two terms, we need to eliminate the last one. To do that you simply subtract 4:
\n" ); document.write( "\"%28x%2B2%29%5E2-4\"
\n" ); document.write( "And finally place the last term right after that.
\n" ); document.write( "\"%28x%2B2%29%5E2-4-1=%28x%2B2%29%5E2-5\" This means the vertex is (-2,-5)\r
\n" ); document.write( "\n" ); document.write( "3) Same as the first one, and to make a quadratic function \"open down\" you will need to put a negative sign before the bracket:
\n" ); document.write( "\"-%28x%2B2%29%5E2%2B7\"
\n" ); document.write( "or
\n" ); document.write( "\"7-%28x%2B2%29%5E2\" \n" ); document.write( "
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