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Let 
f(x)=sqrt(x+9) and let 
c be the number that satisfies the Mean Value Theorem for 
f on the interval 
[0,16].
What is 
c ?
Choose 1 answer:
(A) 16
(B) 43
(C) 55
(D) 7

Let f(x)=x+9 f(x)=\sqrt{x+9} and let c c be the number that satisfies the Mean Value Theorem for f f on the interval [0,16] [0,16] .\newlineWhat is c c ?\newlineChoose 11 answer:\newline(A) 1616\newline(B) 4343\newline(C) 5555\newline(D) 77

Full solution

Q. Let f(x)=x+9 f(x)=\sqrt{x+9} and let c c be the number that satisfies the Mean Value Theorem for f f on the interval [0,16] [0,16] .\newlineWhat is c c ?\newlineChoose 11 answer:\newline(A) 1616\newline(B) 4343\newline(C) 5555\newline(D) 77
  1. Statement of Theorem: The Mean Value Theorem states that if a function ff is continuous on the closed interval [a,b][a, b] and differentiable on the open interval (a,b)(a, b), then there exists at least one number cc in the interval (a,b)(a, b) such that f(c)=f(b)f(a)baf'(c) = \frac{f(b) - f(a)}{b - a}. We need to apply this theorem to the function f(x)=x+9f(x) = \sqrt{x+9} on the interval [0,16][0, 16].
  2. Function Analysis: First, we need to ensure that the function f(x)=x+9f(x) = \sqrt{x+9} is continuous on [0,16][0, 16] and differentiable on (0,16)(0, 16). Since the square root function is continuous and differentiable for all non-negative values of its argument, and x+9x+9 is non-negative for all xx in [0,16][0, 16], f(x)f(x) is indeed continuous on [0,16][0, 16] and differentiable on (0,16)(0, 16).
  3. Calculate f(0)f(0) and f(16)f(16): Next, we calculate f(0)f(0) and f(16)f(16). \newlinef(0)=0+9=9=3f(0) = \sqrt{0+9} = \sqrt{9} = 3\newlinef(16)=16+9=25=5f(16) = \sqrt{16+9} = \sqrt{25} = 5
  4. Calculate Average Rate of Change: Now, we calculate the average rate of change of f(x)f(x) on the interval [0,16][0, 16]:(f(16)f(0))/(160)=(53)/(160)=2/16=1/8(f(16) - f(0)) / (16 - 0) = (5 - 3) / (16 - 0) = 2 / 16 = 1/8
  5. Find Derivative of f(x)f(x): To find cc, we need to find the value of xx for which the instantaneous rate of change, f(x)f'(x), is equal to the average rate of change, 18\frac{1}{8}. First, we find the derivative of f(x)f(x):f(x)=ddx[x+9]=12x+9f'(x) = \frac{d}{dx} [\sqrt{x+9}] = \frac{1}{2\sqrt{x+9}}
  6. Set Derivative Equal to Average Rate of Change: We set the derivative equal to the average rate of change and solve for xx:12x+9=18\frac{1}{2\sqrt{x+9}} = \frac{1}{8}Multiplying both sides by 2x+92\sqrt{x+9} gives:1=2x+981 = \frac{2\sqrt{x+9}}{8}Multiplying both sides by 88 gives:8=2x+98 = 2\sqrt{x+9}Dividing both sides by 22 gives:4=x+94 = \sqrt{x+9}
  7. Solve for x: Squaring both sides to eliminate the square root gives:\newline16=x+916 = x + 9\newlineSubtracting 99 from both sides gives:\newlinex=169x = 16 - 9\newlinex=7x = 7
  8. Verify cc Value: We have found that c=7c = 7 satisfies the Mean Value Theorem for the function f(x)f(x) on the interval [0,16][0, 16].

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