2 [3] = 8 can also be expressed as log [2] 8 = 3
Is this correct?
0.035 [x] = 2.74 Find x?
- Re-express as a log which is log [0.035] 2.74 = x
- Draw line
- log 2.74__ = x
log 0.035
Or is this correct?
0.035 [x] = 2.74 Find x?
- Log both sides
log 0.035 [x] = log 2.74 - Re-express to remove power
x log 0.035 = log 2.74
- Make x the subject of the equation
x = log 2.74 / log 0.035
34 comments:
Please excuse the layout of the powers. Subscript or superscript is not allowed
Hello, I tried to figure out the first set of statements of the blog and didn't get anywhere. My answers are not looking right but I will still try again. If there's any way it can be revised (maybe in words)please do so,thanks!
I looked at the other two scenarios below and I think that both are along the same lines; just two different methods. I reasoned with both options and I recognised that first option follows the steps to the rule of log ab=c while the other is another method that I learnt in class. I'm assuming that whatever you do on the left you also do on the right and then make x the subject of the formula. I have the applications of both methods in my notes. The steps in option 2 are more logical though,that's just my view. P.S. I didn't do Add maths and I'm not very keen on the subject so I need as much guidance as I can get. I will appreciate any comment to indicate if I'm on the right track.
don't worry sweediekinks, u had it figure out all the time........ up to a point. i fully agree with what u said about option 2, caused it should be known by all that do maths, that in any equation what every u do on one side of the equation , u must do the same to the other side of the equation to for the equation to be balance off. your concept of making x the subject of the formula was also correct, but i don't really agree with u about your "choice" of option 1. i don't know if im wrong but i don't think taking log twice on one side of the equation surely doesn't "balance" the equation, if u know where i am coming from.i may have mis-interpreted the equation ....... so can someone correct me if i'm wrong. thanks in advance.
mummy!! im abit confused by ur first option in this question. I understand ur second option though and it makes perfect sense. wats there to explain. The steps are all there. Cookie!!! watever u do on one side of an equation u must do on d other. Just accept that. Its jus a rule ok.
i really not sure how correct the first method is but the second method is what i am accustomed to.according to matser cookie 'what is done on the right side must be done on the left side of the equation........ but i have this unusual feeling in my head telling me that the first option is incorrect.
can someone explain mummy's first option for me please??? i jus dont get it!!!!
I think that these questions are quite sraight forward!the working is there, the concept is there; you just need to know your logarithmic laws.
yes miss the second part is coorect taking logs on both sides of the equation allows u to isolate the power (which is X) by evetually making it the subject of the formula the answer is 0.438/-1.456 equlling to - .03008
i dont really understand the first part but the second one makes send where dividin the log over the number by the log of the base to find the powers
both the first method and the second method are correct. i remembered miss teaching us to draw a line and and separate the base from the other number. place logs infront of them, using the base number as the denomenator and the other number as the numerator. which was done the first method
hi, miss i don't seem to understand.
can the formula be expressed in the form of an indice or exponent and then solve for x
i understand how the first equation that was written works, but the last part i can't really understand. help....
I think I understand the first part and the first and second methods are indeed correct I clearly remembered when miss showed us about drawing the line to seperate the the base from the numbers.Then you wud place logs on both sides of the equation.
cruiser you are almost correct. just one problem, you dont use logs on both sides in this case. you apply logs above and below the division sign.
thanks poison you say I can only apply logs above and below .ok I think I understand
obviously the second option would be the correct.
I think both methods are corrrect. They both have the proper functions of logs applied but i do prefer the first method
i finally get the hang of option 1..so what u tryn to say is
log[a]b is the same as log b/log a. i kno for a fact that dat is correct!!!
i agree with yoshi i think that the second option is correct because the most logical thing to do would be to take logs on both sides before proceeding. i maybe wrong but that is my opinion. correct me if i'm wrong.
i agree with the second option, i totally understand maybe cause its quite straight forward.The first option is very confusing, someone explain please!!!!!!
this is the master here, i now know what the first option is. it is the famous change of base formula. it states that:
log[a]b can be changed to the form of log[c]b/log[c]a. hope this explain to everyone.
the first method to me is incorrect. the second is more feasable. if the [x] is a superscript, then to solve for x, you need to take logs on both sides.
now looking at things.. both solutions are correct. you will arrive at the same answer.
to arirosa
the first method is not really a law of logs.. fariel showed me that way and it was new to me. you still arrive at the same answer at the end so the method is correct.
what you do is after you convert the equation into the logs
log [0.035] 2.74 = x
the [.035] is to the base of log. you draw a line between the two numbers. this simply shows the 2 numbers that you will divide the logs of
that is
log 2.74 and log 0.035
hope this helps
To cokebaby:
There are two methods shown by miss on the blog, however one is correct and the other is not.
Therefore you have done well by spotting that there is an error in the first method.
To cokebaby:
It can be clearly seen that the first method is completely wrong because x is not the subject of the formula.
The second method is correct as we know in maths, whatever we do on one side of an equation the same must be done on the other side to maintain a balance therefore we take logs on both sides and follow the rule: (log[a}b=c.
Eg. log[a]b => log b/log a.
I know that I'm a bit confusing but thats the way that helps me and I hope it helps you.
To dark angel:
Hi darkangel I saw your comment and would like to assist you but you need to tell me what is it that you don't understand.Only then can I help you.
L8RRZ!
TO WONG FEI HONG:
Is it true that the second method is also correct? If that is so then you have thought me something. I have looked at your response to arirosa and it seems to make sense especially if it was approved by miss fariel. I had no knowledge of that method.
I AM ASKING ANYONE TO SECOND THAT METHOD, IS IT CORRECT?
well i kinda did addmaths as an eight subject but bcuz i started it late i didnt get to write the exam so i kinda kinda not get the jist of the strange world i so totally dont understand the first option if i had to do it i wud have chosen the second option anyone dred i need help xplain hoe u can do it the first way in simple term please i find this aaaallllllll to be grick
To cokebaby:
I am seeing that someone is responding that the second first method is also. If this is so then I am really sorry for confusing you.
TO cokebaby:
In my last post I was really trying to say that someone gave a response saying that the second method is also correct. Therefore previously I have corrected you by saying it is wrong.
Therefore if it is correct I am sorry for confusing you.
i think the both methods are correct however i am positive the second method is accurate cuz i usually use it and get the right answers and according to master cookie in an equation what ever is done on one side of the equation, the same must be done to the other side of the equation for the equation to be balanced off. i also believe the second method is correct aswell since when worked out with both methods the same answer is obtained, -0.3 and in class miss showed us the first method so i guess it is correct and as master cookie said again that this method came from the change of base law. however i'm still a bit confused MASTER COOKIE bcuz i thought that the change of base method was just used to change the base of a logorithm and obtain the same base as another logorithm in the same equation so the equation can be easily solved?
TO LILO: yeah i think it is possible to use indices or exponent however since decimals are involve it may be kind of difficult so maybe thats why logs are used since it will be more simple to work out.
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