- A0
- B1
- C2
- D3
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Correct answer: C
The user wants me to find the total number of local maxima and local minima for the given piecewise function.
Function:
To find the local maxima and minima, we need to find the critical points of the function. Critical points occur where the derivative f'(x) is zero or undefined.
Step 1: Analyze the first piece of the function, for -3 < x <= -1
-
Find the derivative:
-
Find critical points by setting
f'(x) = 0:2 + x = 0x = -2 -
Check if
x = -2is in the interval(-3, -1]: Yes,-3 < -2 <= -1. -
Use the First Derivative Test to classify
x = -2: We examine the sign of aroundx = -2.- For
x < -2(e.g.,x = -2.5), . - For
x > -2(e.g.,x = -1.5), . Sincef'(x)does not change sign atx = -2(it is positive on both sides),x = -2is a point of inflection, not a local maximum or minimum.
- For
Step 2: Analyze the second piece of the function, for -1 < x < 2
-
Find the derivative:
-
Find critical points:
f'(x) = 0: has no solution.f'(x)is undefined when the denominator is zero, which occurs atx = 0.
-
Check if
x = 0is in the interval(-1, 2): Yes,-1 < 0 < 2. -
Use the First Derivative Test to classify
x = 0: We examine the sign of aroundx = 0.- For
x < 0(e.g.,x = -0.1), is negative, sof'(x) < 0. The function is decreasing. - For
x > 0(e.g.,x = 0.1), is positive, sof'(x) > 0. The function is increasing. Sincef'(x)changes from negative to positive atx = 0, the function has a local minimum atx = 0.
- For
Step 3: Analyze the point where the function definition changes, x = -1
Points where the function definition changes can also be local extrema if the function is not differentiable there. We need to check the behavior of the function around x = -1.
-
Check for continuity at
x = -1:- Value at
x = -1: . - Limit from the right: .
Since the value of the function and the limit from the right are equal, the function is continuous at
x = -1.
- Value at
-
Check differentiability at
x = -1(or use the first derivative test across the point):- For
xin(-3, -1), we found . Asxapproaches-1from the left,f'(x)approaches , which is positive. So,f(x)is increasing to the left ofx = -1. - For
xin(-1, 0), we found . Forxin this interval, is negative, sof'(x)is negative. So,f(x)is decreasing to the right ofx = -1.
Since the function is increasing to the left of
x = -1and decreasing to the right,x = -1is a point of local maximum. - For
Step 4: Conclusion
We have found the following:
x = -2is a point of inflection.x = -1is a local maximum.x = 0is a local minimum.
The total number of local maxima and local minima is one maximum plus one minimum, which is 2.
This corresponds to option C.
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