precalculus
posted by marcus on .
log_6(2x + 4)=2?
5 In x=10?
log(x+25)=1+ log(2x7)?

You have to know the logarithm rules and definition
Definition: if log(base a)x=b then x=a^b
RulesI am going to use base 10 but it applies for every base:
1) loga^r=rloga
2)log(a*b)=loga+logb
3)log(a/b)=logalogb
4)change of base: loga=log(base b)a/log(baseb)10
So the first one I don't understand question.
Second: lnx=2 so x=e^2 (by definition)
Third: log(x+25)log(2x7)=1 so by using 3rd law: log[(x+25)/(2x7)]=1 and then definition; 10^1= (x+25)/(2x7) so cross multiplying; 10(2x7)=x+25 so 20x70=x+25 19x=95 x=5
Hope this helps