Examples with solutions for Rules of Logarithms Combined: Using multiple rules

Exercise #1

log7x+log(x+1)log7=log2xlogx \log7x+\log(x+1)-\log7=\log2x-\log x

?=x ?=x

Video Solution

Step-by-Step Solution

Defined domain

x>0

x+1>0

x>-1

log7x+log(x+1)log7=log2xlogx \log7x+\log\left(x+1\right)-\log7=\log2x-\log x

log7x(x+1)7=log2xx \log\frac{7x\cdot\left(x+1\right)}{7}=\log\frac{2x}{x}

We reduce by: 7 7 and by X X

x(x+1)=2 x\left(x+1\right)=2

x2+x2=0 x^2+x-2=0

(x+2)(x1)=0 \left(x+2\right)\left(x-1\right)=0

x+2=0 x+2=0

x=2 x=-2

Undefined domain x>0

x1=0 x-1=0

x=1 x=1

Defined domain

Answer

1 1

Exercise #2

log23x×log58=log5a+log52a \log_23x\times\log_58=\log_5a+\log_52a

Given a>0 , express X by a

Video Solution

Step-by-Step Solution

Answer

2a2273 \sqrt[3]{\frac{2a^2}{27}}

Exercise #3

log4x+log2log9=log24 \log4x+\log2-\log9=\log_24

?=x

Video Solution

Answer

112.5 112.5

Exercise #4

log9e3×(log224log28)(ln8+ln2) \log_9e^3\times(\log_224-\log_28)(\ln8+\ln2)

Video Solution

Answer

6 6

Exercise #5

log45+log423log42= \frac{\log_45+\log_42}{3\log_42}=

Video Solution

Answer

log810 \log_810

Exercise #6

log64×log9x=(log6x2log6x)(log92.5+log91.6) \log_64\times\log_9x=(\log_6x^2-\log_6x)(\log_92.5+\log_91.6)

Video Solution

Answer

For all 0 < x

Exercise #7

Calculate the value of the following expression:

ln4×(log7x7log7x4log7x3+log2y4log2y3log2y) \ln4\times(\log_7x^7-\log_7x^4-\log_7x^3+\log_2y^4-\log_2y^3-\log_2y)

Video Solution

Answer

0 0

Exercise #8

2log78log74+1log43×log29= \frac{2\log_78}{\log_74}+\frac{1}{\log_43}\times\log_29=

Video Solution

Answer

7 7

Exercise #9

log311log34+1ln32log3= \frac{\log_311}{\log_34}+\frac{1}{\ln3}\cdot2\log3=

Video Solution

Answer

log411+loge2 \log_411+\log e^2

Exercise #10

log76log71.53log721log82= \frac{\log_76-\log_71.5}{3\log_72}\cdot\frac{1}{\log_{\sqrt{8}}2}=

Video Solution

Answer

1 1

Exercise #11

3(ln4ln5log57+1log65)= -3(\frac{\ln4}{\ln5}-\log_57+\frac{1}{\log_65})=

Video Solution

Answer

3log5724 3\log_5\frac{7}{24}

Exercise #12

1ln41log810= \frac{1}{\ln4}\cdot\frac{1}{\log_810}=

Video Solution

Answer

32loge \frac{3}{2}\log e

Exercise #13

log3x2log527log58=lne \log_3x^2\log_527-\log_58=\ln e

Video Solution

Answer

±406 \pm\sqrt[6]{40}

Exercise #14

Find X

ln8x×log7e2=2(log78+log7x2log7x) \ln8x\times\log_7e^2=2(\log_78+\log_7x^2-\log_7x)

Video Solution

Answer

For all x>0

Exercise #15

Solve for X:

lnx+ln(x+1)ln2=3 \ln x+\ln(x+1)-\ln2=3

Video Solution

Answer

1+1+8e32 \frac{-1+\sqrt{1+8e^3}}{2}

Exercise #16

log8x3log8x1.5+1log49x×log7x5= \frac{\log_8x^3}{\log_8x^{1.5}}+\frac{1}{\log_{49}x}\times\log_7x^5=

Video Solution

Answer

12 12

Exercise #17

logx16×ln7lnxln4logx49= \log_x16\times\frac{\ln7-\ln x}{\ln4}-\log_x49=

Video Solution

Answer

2 -2

Exercise #18

log47×log149aclog4b= \frac{\log_47\times\log_{\frac{1}{49}}a}{c\log_4b}=

Video Solution

Answer

logbc1a \log_{b^c}\frac{1}{\sqrt{a}}

Exercise #19

log49x+log4(x+4)log43=ln2e+ln12e \log_49x+\log_4(x+4)-\log_43=\ln2e+\ln\frac{1}{2e}

Find X

Video Solution

Answer

2+393 -2+\frac{\sqrt{39}}{3}

Exercise #20

log5x+log5(x+2)+log25log22.5=log37×log79 \log_5x+\log_5(x+2)+\log_25-\log_22.5=\log_37\times\log_79

Video Solution

Answer

1+6 -1+\sqrt{6}