# Writing a function in standard form to find the vertex.

• Oct 12th 2009, 03:47 PM
Isimbot
Writing a function in standard form to find the vertex.
$x^2+8x+11$

For standard form I got $(x+4)^2=5$ but I should have got
$(x-4)^2=-5$

according to the vertex formula:

-b/2a
• Oct 12th 2009, 03:59 PM
mr fantastic
Quote:

Originally Posted by Isimbot
$x^2+8x+11$

For standard form I got $(x+4)^2=5$ but I should have got
$(x-4)^2=-5$ Mr F says: No, see below.

according to the vertex formula:

-b/2a

$y = a(x - h)^2 + k$ has a vertex at x = h. Your vertex formula told you that x = -8/2 = -4 therefore h = -4 which agrees with your earlier (correct) calculation.