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Multiple Choice
Which of the following definite integrals is equal to ?
A
B
C
D
Verified step by step guidance
1
Step 1: Recognize that the given limit represents a Riemann sum. A Riemann sum is a way to approximate the value of a definite integral by summing up areas of rectangles under a curve. The general form of a Riemann sum is lim_{n \to \infty} \sum_{k=1}^{n} f(x_k) \Delta x, where \Delta x is the width of each subinterval and f(x_k) is the function evaluated at a sample point in each subinterval.
Step 2: Identify the components of the given Riemann sum. Here, \Delta x = \frac{10}{n}, which represents the width of each subinterval. The term \left(1 + \frac{5k}{n}\right)^2 corresponds to the function being integrated, and the interval of integration can be inferred from the range of x values covered by the sum.
Step 3: Determine the interval of integration. The term \left(1 + \frac{5k}{n}\right) suggests that the x-values range from 1 (when k=1) to 6 (when k=n). This means the definite integral will be evaluated over the interval [1, 6].
Step 4: Write the function being integrated. The given Riemann sum includes the term \left(1 + \frac{5k}{n}\right)^2, which corresponds to the function f(x) = 50x^2 when multiplied by the constant factor 50 (from the term 5n). Thus, the integral represents \int_{1}^{6} 50x^2 \, dx.
Step 5: Conclude that the correct answer is \int_{1}^{6} 50x^2 \, dx, as this matches the function and interval derived from the Riemann sum.