The exponential function is
.
Observe the graph :
\The graph passes through the points
and
.
Substitute above points
and
in the function
to find the
value.
First substitute point
in
.

Substitute point
in
.
Solve the equations
and
.
Multiply the equations
by
.
.
Multiply the equations
by
.
.
Therefore,
\
Logarithmic definition :
.

.
Consider
.
Substitute
in
.

Substitute
and
in
.

.
.