Showing posts with label Logarithmic Equations. Show all posts
Showing posts with label Logarithmic Equations. Show all posts

Tuesday, December 30, 2014

solve the equation ln(x)- ln (x-3) = ln(5)

combining logs...
ln%28x%2F%28x-3%29%29=ln%285%29


raising e to both sides of the equation...
%0D%0Ax%2F%28x-3%29=5%0D%0A
which leads to...

x=5%28x-3%29
x=5x-15
4x=15
and so...

x=15%2F4

Solve: log(x+4) + log(x)=9



Combining into one log...


log%28%28%28x%2B4%29%28x%29%29%29=9

raise 10 to both sides of the equation...
x%5E2%2B4%2Ax=10%5E9

x%5E2%2B4%2Ax-1000000000=0
After solving we note that only positive numbers are solutions (Why?)

x%5B1%5D=-2+%2B+82%2A+sqrt%28148721%29

Sunday, November 10, 2013

Solve: 2ln3x+ln2=lnx

ln2=lnx-2ln3x
lnx-2ln3x=ln2
ln(x/(3x)^2)=ln2
e^ln(x/(3x)^2)=e^ln2
x/(9x^2)=2
1/(9x)=2
x=1/18