Question

Solve 9^x + 4 = 11 for x using the change of base formula log base b of y equals log y over log b.

Answer 1

Answer:

If you meant $9^x+4=11$, then the answer is approximately 0.866.

If you meant $9^{x+4}=11$, then the answer is approximately -2.909 which looks like what you meant based on the choices.

Step-by-step explanation:

$9^x+4=11$

First step is to get the exponential part by itself. The part that has the variable exponent which is the $9^x$ term.

To do this we need to subtract 4 on both sides:

$9^x=11-4$

Simplify:

$9^x=7$

The equivalent logarithmic form is:

$\log_9(7)=x$

I always say to myself the logarithm is the exponent that is how I know what to put opposite the side containing the log.

Anyways if you don't have options for computing $\log_b(a)$ in your calculator you need to use the change of base formula.

$\frac{\log(7)}{\log(9)}=x$

So $x \approx 0.8856$

I don't see this as a choice so maybe you actually meant the following equation:

$9^{x+4}=11$

Let's see if this is the correct interpretation.

So the exponential part is already isolated.

So we just need to put in the equivalent logarithmic form:

$\log_9(11)=x+4$

Now we subtract 4 on both sides:

$\log_9(11)-4=x$

Again if you don't have the option for computing $\log_b(a)$ in your calculator, you will have to use the change of base formula:

$\frac{\log(11)}{\log(9)}-4=x$

$x \approx -2.909$