davidmazzei
New member
- Joined
- Jun 19, 2023
- Messages
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You can check your answer to any "solving" problem by plugging your answer back into the original exercise. If you plug [imath]2.77[/imath] in for [imath]x[/imath], what do you get?Im studying for my engineering license and I dont remember how to do math (oh the irony). This is an engineering economics problem that ends up having x's in the exponent's and I keep getting the wrong answer. See below for my work.
Thank you!!
View attachment 36019
As I understand it, you got 3.58, but your source says 2.77?Im studying for my engineering license and I dont remember how to do math (oh the irony). This is an engineering economics problem that ends up having x's in the exponent's and I keep getting the wrong answer. See below for my work.
Thank you!!
View attachment 36019
Really? I didn't know that you even needed a rule to take the log of a sum. Personally, I just compute the log of the sum....and there is no rule that allows you to take the log of a sum
Can you differentiate the LHS of the given equation?Im studying for my engineering license and I dont remember how to do math (oh the irony). This is an engineering economics problem that ends up having x's in the exponent's and I keep getting the wrong answer. See below for my work.
Thank you!!
View attachment 36019
I am assuming you are saying that with your tongue firmly planted in your cheek.Really? I didn't know that you even needed a rule to take the log of a sum.
I question that. If d=b+c, then loga(b+c) = logad. That is the rule, just add b and c and compute the log of that.I am assuming you are saying that with your tongue firmly planted in your cheek.
Just for clarification, I think the "law" being referred to is the "law of log of a product" where
Loga(b*c) = Logab + Logac .....(with usual restrictions)
There is no "corresponding" law for Loga(b+c)
I took what you said to be a joke (tongue in cheek, that is), pretending not to recognize slightly informal language.Really? I didn't know that you even needed a rule to take the log of a sum. Personally, I just compute the log of the sum.
I meantWhen you take the log of both sides, you have to follow rules to simplify; and there is no rule that allows you to take the log of a sum. You can't just take the log of each term, as you have done.
"Take", in context, doesn't mean "calculate" -- that isn't what he was doing! He was rewriting an expression. And there is no rule that allows you to rewrite the log of a sum as a sum of logs.When you simplify the log of both sides, you have to follow rules to simplify; and there is no rule that allows you to simplify the log of a sum. You can't just take the log of each term, as you have done.
Are you saying that computing the log is a "rule" corresponding to the rule he quoted, "Loga(b*c) = Logab + Logac" ? I don't think so.I question that. If d=b+c, then loga(b+c) = logad. That is the rule, just add b and c and compute the log of that.
Dr Peterson clearly [said] that there is no rule that allows you to take the log of a sum. To me that means that you can't compute the log of a sum. After all, if you could, then there would be a rule.