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Let ff be the function defined by f(a)=01(2z215z2)dtf(a)=\int_{0}^{1}(2z^{2}-15z^{2})\,dt. On which of the following intervals is the graph of y=f(x)y=f(x) concave down?\newline(A) (,0)(-\infty,0) only\newline(B) (,2)(\rightarrow \infty,2)\newline(C) (0,)(0,\infty)\newline(D) (2,3)(2,3) only\newline(E) (3,)(3,\infty) only

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Q. Let ff be the function defined by f(a)=01(2z215z2)dtf(a)=\int_{0}^{1}(2z^{2}-15z^{2})\,dt. On which of the following intervals is the graph of y=f(x)y=f(x) concave down?\newline(A) (,0)(-\infty,0) only\newline(B) (,2)(\rightarrow \infty,2)\newline(C) (0,)(0,\infty)\newline(D) (2,3)(2,3) only\newline(E) (3,)(3,\infty) only
  1. Identify Function: Identify the function inside the integral.\newlineReasoning: The function given inside the integral is 2z215z+22z^2 - 15z + 2.\newlineCalculation: No calculation needed here.
  2. Calculate Integral: Calculate the integral of the function from 00 to 11.\newlineReasoning: To find f(x)f(x), we need to integrate the quadratic function.\newlineCalculation: 01(2z215z+2)dz=[23z3152z2+2z]01=(23152+2)(0)=237.5+2=2.83 \int_0^1 (2z^2 - 15z + 2) \, dz = \left[\frac{2}{3}z^3 - \frac{15}{2}z^2 + 2z\right]_0^1 = \left(\frac{2}{3} - \frac{15}{2} + 2\right) - (0) = \frac{2}{3} - 7.5 + 2 = -2.83 .
  3. Determine Second Derivative: Determine the second derivative of the function.\newlineReasoning: Concavity is determined by the second derivative of the function.\newlineCalculation: Since f(x)f(x) is a constant (as the integral of a function over a fixed interval results in a constant), f(x)=0f''(x) = 0.
  4. Analyze Concavity: Analyze the second derivative to find concavity.\newlineReasoning: A function is concave down where its second derivative is less than 00.\newlineCalculation: Since f(x)=0f''(x) = 0 everywhere, there are no intervals where the function is concave down.

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