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Find the average value fave f_{\text{ave}} of the function f f on the given interval.\newlinef(x)=3x2+4x,[1,2] f(x)=3x^{2}+4x, \quad [-1,2]

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Q. Find the average value fave f_{\text{ave}} of the function f f on the given interval.\newlinef(x)=3x2+4x,[1,2] f(x)=3x^{2}+4x, \quad [-1,2]
  1. Define Average Value Formula: To find the average value of a continuous function f(x)f(x) on the interval [a,b][a, b], we use the formula:\newlinefave=1(ba)abf(x)dxf_{\text{ave}} = \frac{1}{(b-a)} \int_{a}^{b} f(x) \, dx\newlineIn this case, f(x)=3x2+4xf(x) = 3x^2 + 4x and the interval is [1,2][-1, 2].
  2. Calculate Definite Integral: First, we need to calculate the definite integral of f(x)f(x) from 1-1 to 22.12(3x2+4x)dx\int_{-1}^{2} (3x^2 + 4x) \, dxThis requires us to integrate the function term by term.
  3. Evaluate Antiderivative: The integral of 3x23x^2 with respect to xx is x3x^3, and the integral of 4x4x with respect to xx is 2x22x^2.\newlineSo, (3x2)dx=x3\int(3x^2) \, dx = x^3 and (4x)dx=2x2\int(4x) \, dx = 2x^2.
  4. Subtract Lower Limit: Now we can write the antiderivative of f(x)f(x):(3x2+4x)dx=x3+2x2+C,\int(3x^2 + 4x) dx = x^3 + 2x^2 + C, where CC is the constant of integration. However, since we are calculating a definite integral, we do not need to include CC.
  5. Simplify Expression: We evaluate the antiderivative at the upper and lower limits of the interval and subtract: \newline(23+2(22))((1)3+2(1)2)(2^3 + 2\cdot(2^2)) - ((-1)^3 + 2\cdot(-1)^2)\newlineThis simplifies to (8+8)(1+2)(8 + 8) - (-1 + 2).
  6. Find Average Value: Simplifying the expression gives us:\newline(16)(1)(16) - (1)\newlineWhich equals 1515.
  7. Divide by Interval Length: Now we have the definite integral of f(x)f(x) from 1-1 to 22, which is 1515. To find the average value, we divide this result by the length of the interval, which is 2(1)=32 - (-1) = 3.
  8. Calculate Average Value: The average value of the function f(x)f(x) on the interval [1,2][-1, 2] is: fave=13×15f_{\text{ave}} = \frac{1}{3} \times 15
  9. Calculate Average Value: The average value of the function f(x)f(x) on the interval [1,2][-1, 2] is: fave=13×15f_{\text{ave}} = \frac{1}{3} \times 15 Simplifying the expression gives us: fave=5f_{\text{ave}} = 5

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