Cambridge Additional Mathematics

144 Logarithms (Chapter 5)

EXERCISE 5E.2

1 Write as a single logarithm or integer:

a ln 15 + ln 3 b ln 15¡ln 3 c ln 20¡ln 5

d ln 4 + ln 6 e ln 5 + ln(0:2) f ln 2 + ln 3 + ln 5

g 1 + ln 4 h ln 6¡ 1 i ln 5 + ln 8¡ln 2

j 2 + ln 4 k ln 20¡ 2 l ln 12¡ln 4¡ln 3

2 Write in the form lna, a 2 Q :

a 5ln3+ln4 b 3 ln 2 + 2 ln 5 c 3ln2¡ln 8

d 3ln4¡2ln2 e^13 ln 8 + ln 3 f^13 ln( 271 )

g ¡ln 2 h ¡ln(^12 ) i ¡2ln(^14 )

Example 18 Self Tutor

Show that:

a ln

¡ 1

9

¢

=¡2ln3 b ln

³

e

4

́

=1¡2ln2

a ln

¡ 1

9

¢

=ln(3¡^2 )

=¡2ln3

b ln

³

e

4

́

=lne¡ln 4

=lne^1 ¡ln 2^2

=1¡2ln2

3 Show that:

a ln 27 = 3 ln 3 b ln

p

3=^12 ln 3 c ln( 161 )=¡4ln2

d ln(^16 )=¡ln 6 e ln

³

p^1

2

́

=¡^12 ln 2 f ln

³e

5

́

=1¡ln 5

4 Show that:

a ln^3

p

5=^13 ln 5 b ln( 321 )=¡5ln2

c ln

μ

1

p (^52)
¶
=¡^15 ln 2 d ln
μ
e^2
8
¶
=2¡3ln2

Example 19 Self Tutor

Write the following equations without logarithms:

a lnA=2lnc+3 b lnM=3a¡ln 2

a lnA=2lnc+3

) lnA=lnc^2 +lne^3

) lnA=ln(c^2 e^3 )

) A=c^2 e^3

b lnM=3a¡ln 2

) lnM=lne^3 a¡ln 2

) lnM=ln

μ

e^3 a

2

¶

) M=^12 e^3 a

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Additional Mathematics
Y:\HAESE\CAM4037\CamAdd_05\144CamAdd_05.cdr Tuesday, 21 January 2014 2:49:34 PM BRIAN