document.write( "Question 266543: If given a picture of the graph, the vertex of (-1, 5) and another set of points, (2, -13), how do you write the equation in vertex form, f(x) = a(x-h)^2 +k? I know part of the equation is f)x) = a(x+1)^2 +5, but how do I find the \"a\". \n" ); document.write( "

Algebra.Com's Answer #195830 by drk(1908) $\"\"$ $\"About$

You can put this solution on YOUR website!
You are on the right track. We start with
\n" ); document.write( "(i) $\"f%28x%29+=+a%28x%2B1%29%5E2+%2B5\"$
\n" ); document.write( "we are given the point (2,-13)
\n" ); document.write( "put that into (i) and we can see the only variable is \"a\". We get
\n" ); document.write( "(ii) $\"-13+=+a%282%2B1%29%5E2+%2B5\"$
\n" ); document.write( "simplify the right to get
\n" ); document.write( "(iii) $\"-13+=+9a+%2B+5\"$
\n" ); document.write( "subtract to get
\n" ); document.write( "(iv) $\"-18+=+9a\"$
\n" ); document.write( "divide to get
\n" ); document.write( " (v) $\"a+=+-2\"$
\n" ); document.write( "so we get our answers as
\n" ); document.write( "(vi) $\"f%28x%29+=+-2%28x%2B1%29%5E2+%2B5\"$ \n" ); document.write( "

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