Question 1071462
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This procedure is called "completing the square".


<pre>
  {{{-x^2 +6x+c}}} = 

= {{{(-x^2 + 6x) + c}}} = 

= {{{(-x^2 + 2*3*x - 3^2)}}} + {{{3^2 +c}}} = 

= {{{-(x^2 -2*3*x+3^2)}}} + {{{9+c}}} = 

= {{{-(x-3)^2 + (9+c)}}}.


Solved:  h = 3,  k = 9+c.
</pre>