Examples with solutions for The Sum of Logarithms: 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

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

Video Solution

Answer

log810 \log_810

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

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 #6

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

Video Solution

Answer

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

Exercise #7

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

Given a>0 , express X by a

Video Solution

Answer

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

Exercise #8

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 #9

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 #10

(2log32+log3x)log23log2x=3x7 (2\log_32+\log_3x)\log_23-\log_2x=3x-7

x=? x=\text{?}

Video Solution

Answer

3 3

Exercise #11

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 #12

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}

Exercise #13

Given 0<a , find X:

log2ae7(lna+ln4a)=log4xlog4x2+log41x+1 \log_{2a}e^7(\ln a+\ln4a)=\log_4x-\log_4x^2+\log_4\frac{1}{x+1}

Video Solution

Answer

12+1+4132 -\frac{1}{2}+\frac{\sqrt{1+4^{-13}}}{2}

Exercise #14

logx4+logx30.25xlogx11+x=3 \frac{\log_x4+\log_x30.25}{x\log_x11}+x=3

x=? x=\text{?}

Video Solution

Answer

2 2

Exercise #15

logaxlogbylogc2=(logay3logay2)(logb12+logb22)logc(x2+1) \log_ax\log_by\log_c2=(\log_ay^3-\log_ay^2)(\log_b\frac{1}{2}+\log_b2^2)\log_c(x^2+1)

Video Solution

Answer

No solution

Exercise #16

log59(log34x+log3(4x+1))=2(log54a3log52a) \log_59(\log_34x+\log_3(4x+1))=2(\log_54a^3-\log_52a)

Given a>0 , find X and express by a

Video Solution

Answer

18+1+8a28 -\frac{1}{8}+\frac{\sqrt{1+8a^2}}{8}