To determine the maximum of the given function means to
find the vertex of a parabola.
We'll write the function
as:
f(x) = a(x-h)^2 + k, where the vertex has the
coordinates v(h,k)
We'll re-write the given
function:
f(x) = 1(x^2 - 1x) - 6
We'll
complete the square:
x^2 -2*(1/2) x + (1/2)^2 = (x -
1/2)^2
So, we'll add and subtract the value
1/4:
f(x) = 1(x^2 - x + 1/4) - 1/4 -
6
We'll combine like terms outside the
brackets:
f(x) = (x - 1/2)^2 -
25/4
We'll compare the result with the standard form and
we'll get the coordinates of the vertex:
(x - 1/2)^2 -
25/4 = a(x-h)^2 + k
h = 1/2
k
= -25/4
The coordinates of the vertex are:V
(1/2 ; -25/4)
Another way to determine the
local extreme of the function is to use the first derivative of the function (the vertex
is a local extreme).
f'(x) = 2x -
1
We'll determine the critical value of
x:
2x - 1 = 0
2x =
1
x = 1/2
Now, we'll calculate
the y coordinate of the local extreme:
f(1/2) = (1/2)^2 -
1/2 - 6
f(1/2) = 1/4 - 1/2 -
6
f(1/2) =
(1-2-24)/4
f(1/2) =
-25/4
We notice that the
vertex of the function is located in the 4th
quadrant.
No comments:
Post a Comment