Thursday, July 24, 2014

f(x)= e^(3x)-k, where k is a constant that is greater than 0. what is f^-1(x)? what is the domain of f^-1(x) ?

Given that f(x) = e^(3x) -
k


We need to find the inverse function f^-1
(x)


Let f(x) = y


==> y=
e^(3x) - k


Now we will add k to both
sides.


==? y+k = e^(3x)


Now we
will apply the natural logarithm for both sides.


==>
ln (y+k) = ln e^3x


==> ln (y+k) = 3x ln
e


But ln e = 1


==> ln
(y+k) = 3x


Now we will divide by
3.


==> x= ln(y+k) /
3


Now we will rewrite x as
y.


==> y= ln (x+k) /
3


Then the inverse function is
:


f^-1 (x) = (1/3) * ln (x+k)


Now we will find the
domain.


We know that the domain is when (x+k) >
0


But we know that k>
0


Then the domain are x values such that x >
-k


Then the domain is x E ( -k,
inf)

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