Key Concepts and Formulas
- Extreme Value Theorem: A continuous function on a closed interval [a,b] attains both an absolute maximum and an absolute minimum on that interval.
- Critical Points: Points where the derivative of a function is zero or undefined.
- Product Rule: dxd(uv)=u′v+uv′
Step-by-Step Solution
Step 1: Find the derivative of f(x)
We are given the function f(x)=(x+3)2(x−2)3 and we want to find its derivative, f′(x), to locate critical points. We will use the product rule, where u=(x+3)2 and v=(x−2)3.
u′=dxd(x+3)2=2(x+3)
v′=dxd(x−2)3=3(x−2)2
Applying the product rule:
f′(x)=u′v+uv′=2(x+3)(x−2)3+(x+3)2⋅3(x−2)2
Now, we factor out the common terms (x+3) and (x−2)2:
f′(x)=(x+3)(x−2)2[2(x−2)+3(x+3)]
f′(x)=(x+3)(x−2)2[2x−4+3x+9]
f′(x)=(x+3)(x−2)2[5x+5]
f′(x)=5(x+3)(x−2)2(x+1)
The derivative is f′(x)=5(x+3)(x−2)2(x+1).
Step 2: Find the critical points
Critical points occur where f′(x)=0 or f′(x) is undefined. Since f′(x) is a polynomial, it is defined for all real numbers. Thus, we only need to solve f′(x)=0:
5(x+3)(x−2)2(x+1)=0
This gives us the following critical points:
- x+3=0⟹x=−3
- (x−2)2=0⟹x=2
- x+1=0⟹x=−1
The critical points are x=−3,−1,2. All these points lie within the interval [−4,4].
Step 3: Evaluate f(x) at the critical points and endpoints
We need to evaluate f(x)=(x+3)2(x−2)3 at the critical points x=−3,−1,2 and the endpoints x=−4,4.
- f(−4)=(−4+3)2(−4−2)3=(−1)2(−6)3=1⋅(−216)=−216
- f(−3)=(−3+3)2(−3−2)3=(0)2(−5)3=0
- f(−1)=(−1+3)2(−1−2)3=(2)2(−3)3=4⋅(−27)=−108
- f(2)=(2+3)2(2−2)3=(5)2(0)3=25⋅0=0
- f(4)=(4+3)2(4−2)3=(7)2(2)3=49⋅8=392
So we have the following values: f(−4)=−216, f(−3)=0, f(−1)=−108, f(2)=0, and f(4)=392.
Step 4: Identify the maximum (M) and minimum (m) values
From the values calculated in Step 3, we can see that the maximum value is M=392 and the minimum value is m=−216.
Therefore, M−m=392−(−216)=392+216=608.
Common Mistakes & Tips
- Forgetting Endpoints: Always remember to evaluate the function at the endpoints of the interval.
- Sign Errors: Be careful with negative signs when evaluating the function, especially when raising negative numbers to odd powers.
- Factoring: Factoring the derivative simplifies finding the critical points and reduces the risk of algebraic errors.
Summary
To find the maximum and minimum values of the function f(x)=(x+3)2(x−2)3 on the interval [−4,4], we first found the derivative f′(x), then determined the critical points by setting f′(x)=0. We evaluated f(x) at the critical points and the endpoints of the interval. Finally, we identified the maximum and minimum values and calculated their difference, M−m=608.
Final Answer
The final answer is \boxed{608}, which corresponds to option (C).