How do you write in vertex form for $y = x^{2} - 9 x$ $y=x^2 - 9x$ by completing the square?

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Answer 1 · 2015-05-22T14:37:03

Given
$y = x^{2} - 9 x$ $y=x^2-9x$

Completing the square
$y = x^{2} - 9 x + {(\frac{9}{2})}^{2} - {(\frac{9}{2})}^{2}$ $y=x^2-9x+(9/2)^2 - (9/2)^2$

$y = (x - \frac{9}{2}) - \frac{81}{4}$ $y = (x-9/2)-81/4$
which is the vertex form with the vertex at $(\frac{9}{2}, - \frac{81}{4})$ $(9/2,-81/4)$

How do you write in vertex form for y=x2−9xy=x^2 - 9x by completing the square?