Step 1: Recall the formula for the arc length of a curve y = f(x) over the interval [a, b]. The arc length is given by: L = ∫[a, b] sqrt(1 + (dy/dx)^2) dx. Here, f(x) = x^3 / 3 + 1 / (4x), and the interval is [1, 2].
Step 2: Compute the derivative dy/dx of the given function y = x^3 / 3 + 1 / (4x). Use the power rule and the derivative of 1/x. The derivative is: dy/dx = d/dx(x^3 / 3) + d/dx(1 / (4x)) = x^2 + (-1 / (4x^2)).
Step 3: Square the derivative dy/dx to find (dy/dx)^2. This gives: (dy/dx)^2 = (x^2 - 1 / (4x^2))^2. Expand this expression to simplify it further.
Step 4: Substitute (dy/dx)^2 into the arc length formula. The integrand becomes sqrt(1 + (dy/dx)^2). This results in: L = ∫[1, 2] sqrt(1 + (x^2 - 1 / (4x^2))^2) dx.
Step 5: Evaluate the integral ∫[1, 2] sqrt(1 + (x^2 - 1 / (4x^2))^2) dx. This involves simplifying the integrand and using appropriate techniques such as substitution or numerical methods to compute the exact value. The final result will match one of the provided answers.