1. 6^x=4

6^x=4 ? i have a sudden black out and i can't remember the rule for when solving equations like this one.. to complicate things i'm not allowed to answer with x=log4/log6

2. when two logs are divided they can be written thus:

x= log(4/6)

same as

x= log4 - log6

3. and what about if log isn't allowed to be in the answer at all?

4. Are you familiar with the change of base formula?

5. I don't think so.. it's possible that I am, just that it has a very different name in Swedish.. ^^

6. enter it into a calculator you could also write it as x=log (base 4) *6

could you tell me the question in full?

7. Are you not allowed to use a calculator? If you are then you can find the exact value.

8. here's the kicker.. i'm not allowed to use a calculator ^^ yay (not so much)

^6 log4..

9. Originally Posted by weasley74
6^x=4 ? i have a sudden black out and i can't remember the rule for when solving equations like this one.. to complicate things i'm not allowed to answer with x=log4/log6
Method1:
Initial equation
$\displaystyle 6^x=4$

Take the log of both sides (it doesn't matter what base you use)
$\displaystyle log(6^x)=log(4)$

One of the properties of logs is that if they are the log of a number to a power, they are the same as the power times the log of the number. Meaning $\displaystyle log(6^x)=xlog(6)$ so
$\displaystyle xlog(6)=log(4)$

Divide both sides by log(6)
$\displaystyle x=\frac {log(4)}{log(6)}$

Method2
Initial equation
$\displaystyle 6^x=4$

Take log base 6 of both sides
$\displaystyle log_6(6^x) = log_6(4)$

Simlify
$\displaystyle x = log_6(4)$

Use change of base formula to rewrite in a format you can plug into a calculator. Change of base formula says $\displaystyle log_a(b) = \frac{log_c(b)}{log_c(a)}$ This works for any value of c. Typically the value chosen is 10 or e, as log base ten and log base e (natural log) are the two most common logs, and are programmed into any decent calculator.
$\displaystyle x = \frac{log(4)}{log(6)}$

10. Originally Posted by topher0805
Are you not allowed to use a calculator? If you are then you can find the exact value.
$\displaystyle x=\frac{log(4)}{log(6)}$
is the exact value. A decimal value is not exact, it is an approximation, because it cannot get to every digit in the decimal place (if the value is irrational).

11. I thought the poster said you can't answer with log

12. Originally Posted by OzzMan
I thought the poster said you can't answer with log
correct.

13. Originally Posted by OzzMan
I thought the poster said you can't answer with log
Then the answer he is looking for is
$\displaystyle x = \frac{log(4)}{log(6)} \approx$ 0.77370561446908317374049227693595

Which is not exact, and I would seem to require a calculator to find.

It seems most likely to me that they are looking for $\displaystyle x=\frac{log(4)}{log(6)}$ or $\displaystyle x=log_6(4)$ as these values are exact, and one of the other requirements was that he could not use a calculator.

14. What math class is this for? The only way i know how to answer this problem is with logarithms lol. This is interesting.

15. There must be another way to do this without logarithms.

Page 1 of 2 12 Last