1. ## Inversing an equation.

Hi, I need help inversing this function:

y = 2^(x+1) - 3

2. Originally Posted by Tracer
Hi, I need help inversing this function:

y = 2^(x+1) - 3

Swap y with x and x with y to get:

$\displaystyle x = 2^{y+1} - 3$

$\displaystyle x+3 = 2^{y+1}$

$\displaystyle log(x+3) = log(2^{y+1})$

$\displaystyle log(x+3) = (y+1) \mbox{log(2)}$

$\displaystyle \frac{log(x+3)}{log2} = y+1$

$\displaystyle y = \frac{log(x+3)}{log2}-1$

3. Thanks. But I need help with one more thing. I'm confused with the following problems:

You purchase a used car for $8,000. The value of the car decreases 20% each year. Approximatively how much is the car worth in five years? Find the inverse of: f(x) = Lastly; A license plate must have two letters, followed by 3 digits and followed by 2 letters. How many possible license plates are there if letters I and O are excluded and letters and number can be repeated. Thanks. 4. Originally Posted by Tracer Thanks. But I need help with one more thing. I'm confused with the following problems: You purchase a used car for$8,000. The value of the car decreases 20% each year. Approximatively how much is the car worth in five years?

Thanks.
$\displaystyle V(n) = 8000\times 0.8^n$

make $\displaystyle n=5$

Originally Posted by Tracer

Find the inverse of: f(x) =
Like shown in post #2. You need to swap x and y then solve for y.

$\displaystyle y=\sqrt{x-9}$

then

$\displaystyle x=\sqrt{y-9}$

$\displaystyle x^2=y-9$

$\displaystyle x^2+9=y$

$\displaystyle y=x^2+9$

Originally Posted by Tracer
Lastly; A license plate must have two letters, followed by 3 digits and followed by 2 letters. How many possible license plates are there if letters I and O are excluded and letters and number can be repeated.

Thanks.
There are 24 letters and 10 digits available. And they have the order LL DDD LL

What next?

5. Originally Posted by harish21
Swap y with x and x with y to get:

$\displaystyle x = 2^{y+1} - 3$

$\displaystyle x+3 = 2^{y+1}$

$\displaystyle log(x+3) = log(2^{y+1})$

$\displaystyle log(x+3) = (y+1) \mbox{log(2)}$

$\displaystyle \frac{log(x+3)}{log2} = y+1$

$\displaystyle y = \frac{log(x+3)}{log2}-1$
I would say

$\displaystyle x = 2^{y+1} - 3$

$\displaystyle x +3= 2^{y+1}$

$\displaystyle \log_2(x +3)= y+1$

$\displaystyle \log_2(x +3)-1= y$

$\displaystyle y=\log_2(x +3)-1$

6. Thank you guys. I'm doing a final packet - finals are coming up so I just need sample problems. Our book doesn't show ALL of the examples in this packet - I just forgot some. Ummm.

A number is selected from 1 to 50. What is the probability that chosen number is prime given that it is less than 31?

A group has 6 men and 7 women. How many ways can a committee of 2 men and women be formed?

A red die and a blue die are tossed. What is the probability that a red die will show a 6 and the blue die will show an even number?

Sorry I suck at probabilities \:

7. Originally Posted by Tracer

A number is selected from 1 to 50. What is the probability that chosen number is prime given that it is less than 31?
First find the probabilty of getting a prime then find the probabilty of a number less then 31.

What do you get?

8. Originally Posted by pickslides
$\displaystyle V(n) = 8000\times 0.8^n$

make $\displaystyle n=5$
Uhhhh wait where does the 20% go?

And I got uhhh... 10/50 - 1/5

9. Originally Posted by Tracer
Uhhhh wait where does the 20% go?
20% decrease is the same as multiplying something by 80% or 0.8