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Bài tập CALCULUS 24

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Created by T. Madas
Question 91

(***+)

y

y = 4 ( x − 2)

2

A

y = 2 x 2 − 9 x + 16
B
O

x

The figure above shows the graph of the curves with equations

y = 4 ( x − 2)

2

and

y = 2 x 2 − 9 x + 16 .

The curves meet each other at the points A and B .


a) Determine the coordinates of A and B .
b) Find the exact area of the finite region bounded by the two curves, shown
shaded in the above figure.

( )

MP1-E , A ( 0,16 ) B 7 ,9 , 343
2
24

Created by T. Madas


Created by T. Madas
Question 92

(***+)

3x2 − 2 )
(
f ( x) =

2

x2

, x ≠ 0.

Show clearly that




2

f ( x ) dx = 11 .

1

proof

Question 93

(***+)

The curve C has equation

y=

3−8 x
, x>0
x

Show clearly that
d2y
dx

2

=


(

6 1− x
x

3

).
proof

Created by T. Madas


Created by T. Madas
Question 94

(***+)

r

h

A pencil holder is in the shape of a right circular cylinder, which is open at one of its
circular ends.
The cylinder has radius r cm and height h cm and the total surface area of the
cylinder, including its base, is 360 cm 2 .

a) Show that the volume, V cm3 , of the cylinder is given by
V = 180r − 1 π r 3 .
2


b) Determine by differentiation the value of r for which V has a stationary value.
c) Show that the value of r found in part (b) gives the maximum value for V .
d) Calculate, to the nearest cm3 , the maximum volume of the pencil holder.

r=

Created by T. Madas

120

π

≈ 6.18 , Vmax ≈ 742



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