vacancysign wrote:

A few log problems from a study guide that aren't anything close to what is in the book...

1. 8^3x-1 = 20

2. Given that logz2 = 0.333 and logz5 = 0.774, find logz0.4

3. Use change of base formula to solve 2.5^4x = 100

4. Use change of base formula to evaluate expression, then convert it to a logarithm in base 9: log6973

Any and all help is greatly appreciated.

8^3=512, so you get 512x=21, so x=21/512.

Similarly for #3, evaluate 2.5^4 and divide both sides by it to get x.

I'm not seeing why you think you need logs for these, unless you forgot some parentheses.