Forums › Leaving Cert Maths › logs
 This topic is empty.

AuthorPosts


January 12, 2006 at 11:58 pm #13151
log (3x5)+log x=3
2 2

January 12, 2006 at 11:58 pm #388
:log (3x5)+log x=3
2 2

January 13, 2006 at 12:55 am #13152Anonymous
Logarithms
A logarithm is a way of representing a number by the power of a base.
i. addition of logs converts to muliplying using this rule
clck on image to enlarge
to view full explanation click here
log (3x5)(x)
log (3x^25x). multiply out the brackets
Convert log back to numeric format
click image to enlarge
remember: logaM =x means exactly the same thing as saying a^x = M and log means log10 or log to the base power of 10
becomes
10^3= (3x^25x) multiply out the power
1000=(3x^25x)
0=3x^25x 1000
use b+Sqaure root(b^24ac)/2a
where a is coefficient of x^2 (the number with the x^2) ie 3
where b is coefficient of x (the number with the x]) ie 5
and c is the number without an x term
Answer
x=19.12 and 17.44
You should learn the 6 rules relating to logs (they come in useful). I'll post a site if I come across one
Good luck

January 13, 2006 at 4:07 pm #13153

January 13, 2006 at 4:29 pm #13154Anonymous
Properties of Logarithms
Saying that logaM =x means exactly the same thing as saying a^x = M .
the log of the product A*B equals the sum of the logs of A and B
the log of the quotient A/B equals the difference of the logs of A and B.
the log of A to the base a and the power p is equal to p times the log A to the base a
the log of x to the base a is equivilant to the natural log of x divided by the natural log of a. (You would use this rule if you were trying to change the base power)
visit http://hypatia.math.uri.edu/Courses/spring02/mth111/nancy/prlog1.html


AuthorPosts
 You must be logged in to reply to this topic.