Question #322415

Find the global maximum and minimum values of the following function on the given interval. If there are multiple points in a single category list the points in increasing order in x value and enter N in any blank that you don't need to use.

f(x)=4e−x−4e−2x  [0,1]



Global maxima

x = ____ Y=___

x=_____ Y=____

x=____ Y=___

Global minima

x=____ Y=___

x=____ Y=___

x=___ Y=___

x=____ Y=___






1
Expert's answer
2022-04-05T07:15:47-0400
f(x)=4ex4e2x[0,1]f(x)=4ex+8e2xf(x)=4e^{−x}−4e^{−2x} \qquad[0,1]\\ \begin{aligned} f'(x) =& -4e^{-x}+8e^{-2x} \end{aligned}


Find the critical points:


f(x)=0    4ex+8e2x=08e2x=4ex2e2x=ex2=ex/e2x2=exln(2)=x\begin{aligned} f'(x)=0 \implies -4e^{-x}+8e^{-2x}&=0\\ 8e^{-2x}&=4e^{-x}\\ 2e^{-2x}&=e^{-x}\\ 2&=e^{-x}/e^{-2x}\\ 2&=e^{x}\\ \ln(2) &=x \end{aligned}

To find the absolute maximum and absolute minimum, then, we evaluate ff at the critical point and on the endpoints of the interval:

f(ln(2))=4eln(2)4e2ln(2)=4(12)4(14)=21=1\begin{aligned} f(\ln(2))=&4e^{−\ln(2)}−4e^{−2\ln(2)}\\ =&4(\tfrac{1}{2})-4(\tfrac{1}{4})\\ =&2-1\\ =&1 \end{aligned}

f(0)=4e04e0=44=0\begin{aligned} f(0)=&4e^{0}−4e^{0}\\ =&4-4\\ =&0 \end{aligned}

f(1)=4e14e2=4(0.3679)4(0.1353)=1.47160.54120.93\begin{aligned} f(1)=&4e^{−1}−4e^{−2}\\ =&4(0.3679)-4(0.1353)\\ =&1.4716-0.5412\\ \approx&0.93 \end{aligned}

Therefore, ff achieves its absolute minimum of at x=0x=0 and its absolute maximum of 11 at x=ln(2)x= \ln(2)


Thus:

Absolute maxima = 11

Absolute minima =


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