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Let 
f be the function defined by 
f(x)=4sqrtx. If four subintervals of equal length are used, what is the value of the midpoint Riemann sum approximation for 
int_(2)^(8)4sqrtxdx ? Round to the nearest thousandth if necessary.
Answer:

Let f f be the function defined by f(x)=4x f(x)=4 \sqrt{x} . If four subintervals of equal length are used, what is the value of the midpoint Riemann sum approximation for 284xdx \int_{2}^{8} 4 \sqrt{x} d x ? Round to the nearest thousandth if necessary.\newlineAnswer:

Full solution

Q. Let f f be the function defined by f(x)=4x f(x)=4 \sqrt{x} . If four subintervals of equal length are used, what is the value of the midpoint Riemann sum approximation for 284xdx \int_{2}^{8} 4 \sqrt{x} d x ? Round to the nearest thousandth if necessary.\newlineAnswer:
  1. Calculate Subinterval Length: To calculate the midpoint Riemann sum, we first need to determine the length of each subinterval. The interval [2,8][2, 8] has a length of 82=68 - 2 = 6. Since we are using four subintervals, each subinterval will have a length of 6/4=1.56 / 4 = 1.5.
  2. Find Midpoints of Subintervals: Next, we need to find the midpoints of each subinterval. The subintervals are [2,3.5][2, 3.5], [3.5,5][3.5, 5], [5,6.5][5, 6.5], and [6.5,8][6.5, 8]. The midpoints of these subintervals are 2.752.75, 4.254.25, 5.755.75, and 7.257.25, respectively.
  3. Evaluate Function at Midpoints: Now we evaluate the function f(x)=4xf(x) = 4\sqrt{x} at each midpoint. This gives us the values f(2.75)f(2.75), f(4.25)f(4.25), f(5.75)f(5.75), and f(7.25)f(7.25). We calculate these values as follows:\newlinef(2.75)=42.75f(2.75) = 4\sqrt{2.75}\newlinef(4.25)=44.25f(4.25) = 4\sqrt{4.25}\newlinef(5.75)=45.75f(5.75) = 4\sqrt{5.75}\newlinef(7.25)=47.25f(7.25) = 4\sqrt{7.25}
  4. Perform Function Value Calculations: We perform the calculations for each function value:\newlinef(2.75)=42.754×1.6586.632f(2.75) = 4\sqrt{2.75} \approx 4 \times 1.658 \approx 6.632\newlinef(4.25)=44.254×2.0628.248f(4.25) = 4\sqrt{4.25} \approx 4 \times 2.062 \approx 8.248\newlinef(5.75)=45.754×2.3979.588f(5.75) = 4\sqrt{5.75} \approx 4 \times 2.397 \approx 9.588\newlinef(7.25)=47.254×2.69210.768f(7.25) = 4\sqrt{7.25} \approx 4 \times 2.692 \approx 10.768
  5. Calculate Midpoint Riemann Sum: The midpoint Riemann sum is the sum of the function values at the midpoints multiplied by the length of each subinterval. So, we have:\newlineMidpoint Riemann Sum = (f(2.75)+f(4.25)+f(5.75)+f(7.25))×length of subinterval (f(2.75) + f(4.25) + f(5.75) + f(7.25)) \times \text{length of subinterval} \newlineMidpoint Riemann Sum (6.632+8.248+9.588+10.768)×1.5\approx (6.632 + 8.248 + 9.588 + 10.768) \times 1.5
  6. Calculate Sum of Function Values: We calculate the sum of the function values and then multiply by the length of the subinterval:\newlineMidpoint Riemann Sum (6.632+8.248+9.588+10.768)×1.5\approx (6.632 + 8.248 + 9.588 + 10.768) \times 1.5\newlineMidpoint Riemann Sum 35.236×1.5\approx 35.236 \times 1.5\newlineMidpoint Riemann Sum 52.854\approx 52.854
  7. Round Result to Nearest Thousandth: We round the result to the nearest thousandth as requested:\newlineMidpoint Riemann Sum 52.854\approx 52.854 (rounded to three decimal places)