How to solve this?#f:RR#\{2}#->RR;f(x)=x^2/(x-2)#.Demonstrate that #8<=int_3^4f(x)dx<=9#

Answer 1

See below.

We have

#f'(x)=(x^2-4x)/(x-2)^2#

and

#f'(x)# is monotonic increasing for #3 le x le 4#

with

#m_3=f'(3)=-3# #m_4=f'(4)=0#

so

for #3 le x le 4->{(l_i(x)=f(3)+m_3(x-3) le f(x)),(l_s(x)=f(3)+m_4(x-3) ge f(x)):}#
but also defining #l_1(x) = f(4)+m_4(x-3)# and calculating
#x_m= l_i(x) nn l_1(x)=10/3#
we have that #l_2(x) = {(l_i(x), 3 le x le x_m),(l_1(x), x_m lt x le 4):}#

is such that

#l_2(x) le f(x)# for #3 le x le 4# so
#int_3^4 l_2(x)dx le int_3^4f(x)dx le int_3^4l_s(x)dx#

but

#int_3^4 l_2(x)dx=49/6# and #int_3^4 l_s(x)dx=9#

so finally

#8 < 49/6 le int_3^4f(x)dx le 9#
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Answer 2

To solve this problem, we'll first find the integral of ( f(x) ) over the interval ([3, 4]), and then demonstrate that the result falls within the given bounds of ( 8 \leq \int_{3}^{4} f(x) , dx \leq 9 ).

Let's start by finding the integral:

[ \int_{3}^{4} \frac{x^2}{x - 2} , dx ]

We can perform a polynomial division to simplify the integrand:

[ \frac{x^2}{x - 2} = x + 2 + \frac{4}{x - 2} ]

Now, integrate term by term:

[ \int_{3}^{4} x , dx + \int_{3}^{4} 2 , dx + \int_{3}^{4} \frac{4}{x - 2} , dx ]

[ = \frac{x^2}{2} + 2x + 4 \ln|x - 2| \bigg|_{3}^{4} ]

[ = \frac{16}{2} + 2(4) + 4 \ln|4 - 2| - \left(\frac{9}{2} + 2(3) + 4 \ln|3 - 2|\right) ]

[ = 8 + 8 + 4 \ln 2 - \left(\frac{9}{2} + 6 + 4 \ln 1\right) ]

[ = 16 + 4 \ln 2 - \left(\frac{9}{2} + 6\right) ]

[ = 16 + 4 \ln 2 - \frac{21}{2} ]

Now, calculate the exact numerical value:

[ \approx 8.3863 ]

Since ( 8 \leq \int_{3}^{4} f(x) , dx \leq 9 ) is given, and ( 8.3863 ) falls within this range, we've demonstrated that ( 8 \leq \int_{3}^{4} f(x) , dx \leq 9 ).

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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