Q. Let f(x)=2x3+21x2+36x.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
Find Derivative and Critical Points: To find the absolute maximum value of the function on the closed interval −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.
Factor Quadratic Equation: First, we find the derivative of the function f(x)=2x3+21x2+36x, which will give us the critical points where the slope of the tangent is zero or where the derivative does not exist.f′(x)=dxd(2x3+21x2+36x)=6x2+42x+36
Evaluate Function at Critical Points: Next, we find the critical points by setting the derivative equal to zero and solving for x.0=6x2+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+1)(x+6)The solutions are x=−1 and x=−6.
Compare Values: Now we evaluate the function f(x) at the critical points and at the endpoints of the interval.f(−8), f(−6), f(−1), and f(0) need to be calculated.f(−8)=2(−8)3+21(−8)2+36(−8)=−1024+1344−288=32f(−6)=2(−6)3+21(−6)2+36(−6)=−432+756−216=108f(−1)=2(−1)3+21(−1)2+36(−1)=−2+21−36=−17f(0)=2(0)3+21(0)2+36(0)=0
Find Absolute Maximum Value: Comparing the values we calculated, we find that the largest value is f(−6)=108.
Find Absolute Maximum Value: Comparing the values we calculated, we find that the largest value is f(−6)=108.The absolute maximum value of the function f(x) over the closed interval [−8,0] is 108.