Logarithmic functions > Logarithmic functions
12345Logarithmic functions

Solutions to the exercises

Exercise 1
a

Domain: -4 ,
Range:

b

x = -4

c

First shift -4 in the x -direction, then multiply by -3 along the y -axis, and finally shift 1 in the y -direction.

d

1 - 3 log ( x + 4 ) = 0 gives you log ( x + 4 ) = 1 3 and x + 4 = 10 1 3 = 10 3 , so x = 10 3 - 4 .
The intersect is ( 10 3 - 4 , 0 ) .

Exercise 2
a

1 2 log ( x ) = 3 , so x = ( 1 2 ) 3 = 1 8 .

b

2 log ( x ) = -3 , so x = 2 -3 = 1 8 .

c

( 1 8 , -3 )

d

For example ( 2 , -1 ) and ( 2 , 1 ) .

e

h ( x ) = k ( x ) if x = 1 .

f

1 2 log ( x ) = log ( x ) log ( 1 2 ) = log ( x ) log ( 2 -1 ) = log ( x ) - log ( 2 ) = - log ( x ) log ( 2 )
2 log ( x ) = log ( x ) log ( 2 )
This shows that 1 2 log ( x ) = - 2 log ( x ) .

Exercise 3
a

21 = 1 + a log ( 100 ) gives you 21 = 1 + 2 a and therefore a = 10 .

b

See graph.

c

31 = 1 + 10 log ( x ) gives you log ( x ) = 3 and therefore x = 1000 . The answer is thus 1000 ASA.

Exercise 4
a

D f = 0 , , B ( f ) = , vertical asymptote x = 0 .
D ( g ) = , 2 , B g = , vertical asymptote x = 2 .

b

First mirror the graph on the y -axis (or multiply by -1 along the x -axis) and then shift 2 units in the x -direction.

c

x = 2 - x gives you x = 1 .

d

The vertical line x = 1 .

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