Showing posts with label logarithm rule. Show all posts
Showing posts with label logarithm rule. Show all posts

Monday, October 8, 2012

Simplify Logarithm


Introduction for simplify logarithms:

In arithmetic, the logarithms of a number to be a identified base is the power or exponent to which the base have to be raised in order to generate that number. For example, the logarithms of 10000 to the base 100 is 4, because 4 is the power to the which ten must be raised to produce 10000: 104 = 10000, so log1010000  = 4  
                                                          
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Simplify Logarithms Rules:
Product rule: If n, A and B are positive numbers and x ?1, then
Logn(AB) = lognA +lognB

Quotient rule: If A, B and n is positive numbers and n ? 1, then,
log n(`A/B` ) = log nA –logn B

Power rule: If n and A are positive numbers, n ? 1 and m is a real number, then
LognAB =BlognA

Change of base rule: If A, B and n are positive numbers and A ? 1, x ? 1, then
log AB = lognA   *  logBn

Reciprocal rule: If A and B be the positive numbers other than 1, then
logAB =`1/(log_BA) `

Examples for Simplify Logarithms:

Example 1:

Simplify : 56log25+56log26 =56 log2 (6x)

Solution:

logarithmic function56log25+56log26 =56 log2 (6x)

56 log2(5*6) = 56log2(6x)

56log2(30) =56 log2(6x)      by logarithm rule

Equate both sides, s the base are same 2, 6x = 30

x =30/6

x = 5

The answer is x = 5.

Example 2:

Simplify : 44log8512-44log88

Solution:

44log8512 - 44log88 = 44[log8(512/8)]          { by logarithms rule}

= 44log883

= 3*44                         { log88 = 1 }

= 132

The answer is 72.

Example 3:

Simplify logarithms :  12 log289

Solution:

convert the logarithmic equation

=  12log28  { by logarithms rule}

= 12log22 3

= 12*3log22

= 36

The answer is 36.

Example 4:

Simplify : (i) 67 log3 27 - 67log3 9

(ii)56 log5 25 +56  log5 5

Solution:

(i) Since  expression is a sum of two logarithms as well as the bases are equal, we can apply the product rule

(i) 67 log3 27 -48log3 729 = 67[log 3 (27/9)]

= 67 [ log3 (32)]

= 67 log3 32

= 67*2 log33

= 67* 2

= 134

(ii) 56log525+56log5(5)  = 56log5 (25*5)

= 56 log 5(625)

= 56log 5(5^4)

=56log5(54)

= 4*56log55 = 224

Example 5:

Simplify : log6 9x – log6(7x+1)

Solution:

by quotient law, we can write the equations as log6 `((9x) /( 7x+1))` Changing into exponential form, we get

`((9x) / (7x+1))` = 60  = 1

9x = 7x + 1

x = `1/2`