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Let 
f(x)=2x^(3)+21x^(2)+36 x.
What is the absolute maximum value of 
f over the closed interval 
[-8,0] ?
Choose 1 answer:
(A) 0
(B) 108
(C) 180
(D) 32

Let f(x)=2x3+21x2+36x f(x)=2 x^{3}+21 x^{2}+36 x .\newlineWhat is the absolute maximum value of f f over the closed interval [8,0] [-8,0] ?\newlineChoose 11 answer:\newline(A) 00\newline(B) 108108\newline(C) 180180\newline(D) 3232

Full solution

Q. Let f(x)=2x3+21x2+36x f(x)=2 x^{3}+21 x^{2}+36 x .\newlineWhat is the absolute maximum value of f f over the closed interval [8,0] [-8,0] ?\newlineChoose 11 answer:\newline(A) 00\newline(B) 108108\newline(C) 180180\newline(D) 3232
  1. Find Derivative and Critical Points: To find the absolute maximum value of the function on the closed interval 8,0{-8,0}, we need to find the critical points of the function within the interval and evaluate the function at these points and at the endpoints of the interval.
  2. Factor Quadratic Equation: First, we find the derivative of the function f(x)=2x3+21x2+36xf(x) = 2x^3 + 21x^2 + 36x, which will give us the critical points where the slope of the tangent is zero or where the derivative does not exist.\newlinef(x)=ddx(2x3+21x2+36x)=6x2+42x+36f'(x) = \frac{d}{dx} (2x^3 + 21x^2 + 36x) = 6x^2 + 42x + 36
  3. Evaluate Function at Critical Points: Next, we find the critical points by setting the derivative equal to zero and solving for xx.0=6x2+42x+360 = 6x^2 + 42x + 36To solve this quadratic equation, we can factor it or use the quadratic formula. Let's try to factor it first.0=6(x2+7x+6)0 = 6(x^2 + 7x + 6)0=6(x+1)(x+6)0 = 6(x + 1)(x + 6)The solutions are x=1x = -1 and x=6x = -6.
  4. Compare Values: Now we evaluate the function f(x)f(x) at the critical points and at the endpoints of the interval.f(8)f(-8), f(6)f(-6), f(1)f(-1), and f(0)f(0) need to be calculated.f(8)=2(8)3+21(8)2+36(8)=1024+1344288=32f(-8) = 2(-8)^3 + 21(-8)^2 + 36(-8) = -1024 + 1344 - 288 = 32f(6)=2(6)3+21(6)2+36(6)=432+756216=108f(-6) = 2(-6)^3 + 21(-6)^2 + 36(-6) = -432 + 756 - 216 = 108f(1)=2(1)3+21(1)2+36(1)=2+2136=17f(-1) = 2(-1)^3 + 21(-1)^2 + 36(-1) = -2 + 21 - 36 = -17f(0)=2(0)3+21(0)2+36(0)=0f(0) = 2(0)^3 + 21(0)^2 + 36(0) = 0
  5. Find Absolute Maximum Value: Comparing the values we calculated, we find that the largest value is f(6)=108f(-6) = 108.
  6. Find Absolute Maximum Value: Comparing the values we calculated, we find that the largest value is f(6)=108f(-6) = 108.The absolute maximum value of the function f(x)f(x) over the closed interval [8,0][-8,0] is 108108.

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