To find the extreme values of a function, we'll need to
determine the critical alues. The critical values are the roots of the first
derivative.
We'll differentiate the function to determine it's first
derivative.
We'll use the quotient
rule:
f'(x) = [(x^2-4x+5)'*(x+3) -
(x^2-4x+5)*(x+3)']/(x+3)^2
f'(x) = [(2x - 4)*(x+3) -
(x^2-4x+5)]/(x+3)^2
f'(x) = (2x^2 + 6x - 4x - 12 - x^2 + 4x -
5)/(x+3)^2
f'(x) = (x^2 + 6x -
17)/(x+3)^2
We'll put f'(x) = 0
Since
the denominator is always positive, no matter the x value is, we'll determine what values cancel
the numerator.
x^2 + 6x - 17 = 0
We'll
apply quadratic formula:
x1 = [-6+sqrt(36 +
68)]/2
x1 = (-6+sqrt104)/2
x1 =
(-6+2sqrt26)/2
x1 = -3+sqrt26
x2 =
-3-sqrt26
Since we know the critical values, we'll determine the
extreme values:
f(-3+sqrt26) = f(2.09) = (4.36-8.36+5)/(2.09+3) =
9/5.09 = 1.76
f(-3-sqrt26) = f (-8.09) = (65.44+32.36+5)/(-5.09) =
102.8/-5.09 = -20.19
The extreme value are represented
by the pairs: (-3+sqrt26 ; 1.76) and (-3-sqrt26 ; -20.19).
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