# Solving exponential equation using a... graph?

• Aug 9th 2009, 04:49 PM
Såxon
Solving exponential equation using a... graph?
What am I suppose to look for on the graph, in order to solve this?
Sorry if this seems obvious.
Use a graph to solve the equation 2^-x - 6
• Aug 9th 2009, 04:56 PM
skeeter
Quote:

Originally Posted by Såxon
What am I suppose to look for on the graph, in order to solve this?
Sorry if this seems obvious.
Use a graph to solve the equation 2^-x - 6

is the equation supposed to be

$2^{-x} = 6$

???
• Aug 9th 2009, 05:08 PM
Wesker
maybe you mean 2^-x -6=0??
• Aug 9th 2009, 05:10 PM
Såxon
oh wow, sorry yes it is (2^-x) - 6 = 0...
• Aug 9th 2009, 05:15 PM
skeeter
Quote:

Originally Posted by Såxon
oh wow, sorry yes it is (2^-x) - 6 = 0...

you could use a graph on a calculator and calculate the root.

or ...

$2^{-x} = 6$

$\ln(2^{-x}) = \ln(6)$

$-x \cdot \ln(2) = \ln(6)$

$x = -\frac{\ln(6)}{\ln(2)}$