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Bài tập CALCULUS 14

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Created by T. Madas
Question 55

(***)

y

C

O
P

x

The figure above shows the cubic curve C which meets the coordinates axes at the
origin O and at the point P .
The gradient function of C is given by
f ′ ( x ) = 3x 2 − 8 x + 4 .

a) Find an equation for C .
b) Determine the coordinates of P .
C1H , f ( x ) = x3 − 4 x 2 + 4 x , P ( 2,0 )

Created by T. Madas


Created by T. Madas
Question 56

(***)


The point P ( 8,18) lies on the curve C , whose gradient function is given by
dy
= 8 3 x − 10 , x ≥ 0 .
dx
Find an equation for C .
4

C1L , y = 6 x 3 − 10 x + 2

Question 57

(***)

A curve C has equation given by

y=

1 + 3x3
x2

, x≠0

Find the coordinates of the point on C where the gradient is 1.

(1, 4 )

Created by T. Madas


Created by T. Madas

Question 58 (***)
The temperature, T in °C , of a hot drink t minutes after it was made is given by
1
T = 90 − 8t + t 2 , 0 ≤ t ≤ 8 .
2

a) Calculate after how many minutes the drink has a temperature of 60 °C .
b) Find the rate of change of temperature of the drink 4 minutes after it was made.
t = 6 , −4 °C / min

Question 59

(***)

Show clearly that



4

3

3 x−

4
dx = k 3 ,
x

where k is an integer to be found.
k =2


Created by T. Madas



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