Q. Find the average value fave of the function f on the given interval.f(x)=3x2+4x,[−1,2]
Define Average Value Formula: To find the average value of a continuous function f(x) on the interval [a,b], we use the formula:fave=(b−a)1∫abf(x)dxIn this case, f(x)=3x2+4x and the interval is [−1,2].
Calculate Definite Integral: First, we need to calculate the definite integral of f(x) from −1 to 2.∫−12(3x2+4x)dxThis requires us to integrate the function term by term.
Evaluate Antiderivative: The integral of 3x2 with respect to x is x3, and the integral of 4x with respect to x is 2x2.So, ∫(3x2)dx=x3 and ∫(4x)dx=2x2.
Subtract Lower Limit: Now we can write the antiderivative of f(x):∫(3x2+4x)dx=x3+2x2+C, where C is the constant of integration. However, since we are calculating a definite integral, we do not need to include C.
Simplify Expression: We evaluate the antiderivative at the upper and lower limits of the interval and subtract: (23+2⋅(22))−((−1)3+2⋅(−1)2)This simplifies to (8+8)−(−1+2).
Find Average Value: Simplifying the expression gives us:(16)−(1)Which equals 15.
Divide by Interval Length: Now we have the definite integral of f(x) from −1 to 2, which is 15. To find the average value, we divide this result by the length of the interval, which is 2−(−1)=3.
Calculate Average Value: The average value of the function f(x) on the interval [−1,2] is: fave=31×15
Calculate Average Value: The average value of the function f(x) on the interval [−1,2] is: fave=31×15 Simplifying the expression gives us: fave=5
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