Friday, October 1, 2010

Check if the function f(x)= 10x^2 - 2x + 5 as extreme values.

The given function has a single extreme value, namely a
minimum value (bcause the coefficient of x^2 is positive). The minimum value is
represented by the vertex of the parable, whose expression is 10x^2 - 2x +
5.


The coordinates of the vertex are: V(xV ,
yV):


xV = -b/2a


yV =
-delta/4a


delta = b^2 -
4ac


We'll identify the coefficients
a,b,c:


a = 10


b =
-2


c = 5


Now, we'll determine
the coordinates of the vertex:


xV =
-(-2)/2*10


xV =
1/10


xV =
0.1


yV = -(4 -
200)/4*10


yV = 196/4*10


yV =
49/10


yV =
4.9


The function has just one
extreme point and it's coordinates are: (0.1 ,
4.9).


Another manner to verify
the existence and the number of extreme points of a function is to differentiate the
function.


We'll differentiate
f(x).


f'(x) = (10x^2 - 2x +
5)'


f'(x) = 20x - 2


We'll
calculate the roots of f'(x):


f'(x) =
0


20x - 2 = 0


We'll divide by
2:


10x - 1 = 0


x =
1/10


The function has an extreme point for any root of the
derivative.


Since the derivative has just one root, the
function will have just a single extreme point.


f(1/10) =
10/100 - 2/10 + 5


f(1/10) = 1/10 - 2/10 +
5


f(1/10) = -1/10 + 5


f(1/10)
= (-1+50)/10


f(1/10) = 49/10

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