log8(x^2-30)=log8(x)

Question

how to slove this problem

Answer 1

what grade is this for???

Comments

why would that even matter??? don't worry about the grade. if you know it you know it, if not then you don't

Answer 2

 

log8(x^2-30)=log8(x) 

raise both sides to the 8th power to cancel out the log 

your left with x^2-30=x subtract x from both sides 

x^2 - x - 30 =0

(x-6)(x+5) 

x= 6, -5   

now that a property of log allows us to raise it by the base to cancel out the log for example:

log812=1      if we raise both sides to the 8th power it would look like this:

8^log8(12) = 8^1  the 8 and log 8 cancel out 

12=1 which is not correct at all... 8 does not equal 1... hmm mabe i should have thought this problem out more lol but you get the idea :s

 

 

Answer 3

log8's cancel each other

x^2-30 =x

x^2-x-30=0 -- it's a quadratic equation

(x-6)(x+5)=0

x = 6, -5