+0  
 
0
73
1
avatar+175 

Consider the following.

21 − x = 9

(a) Find the exact solution of the exponential equation in terms of logarithms.
 


(b) Use a calculator to find an approximation to the solution rounded to six decimal places.

x =

 Dec 9, 2019
 #1
avatar+106539 
+1

21 - x  =  9       is not an exponential  equation

 

I think this   might be

 

2^(1 - x)  = 9         ???

 

Take the log of both sides

 

log 2 ^(1 - x) =  log 9      and we can write

 

(1 - x) log 2  = log 9       divide both sides by log 2

 

1 - x    =     log 9  / log 2     rearrange as

 

x =  1 -  log 9 / log 2   

 

This is the exact answer in log terms

 

Evaluating with a calculator  we get   ≈  -2.169925

 

 

cool cool cool

 Dec 9, 2019

4 Online Users