## A community for students. Sign up today

Here's the question you clicked on:

## anonymous one year ago Pedro has created the function f(x) = 4x - 3 ------- 2 to represent the number of assignments he has completed, where x represents the number of weeks in the corse. Pedro discovers that, using the inverse function to solve for x = 30, he can predict when he will have 30 assignments completed. Explain to Pedro how to accomplish this, using complete sentences.

• This Question is Closed
1. anonymous

@PeterPan Here it is genius :P

2. anonymous

Essays? But that's so boring -_-

3. anonymous

Tell me about it -_- Thankfully there were only 3, this is my last one.

4. anonymous

Okay, I'm not a good speaker, so I'll give you the gist of it and leave it to you to turn a few sentences into a bloody novel so are you ready? :D

5. anonymous

Sounds good

6. anonymous

To get the inverse of a function Like f(x) = 4x - 16 for instance

7. anonymous

If it wasn't an inverse problem I could do it but I don't understand how to solve inverse problems.

8. anonymous

haha You'll never be able to explain it to Pedro (that's Spanish for Peter, right? :| ) if you don't know it yourself :P So let me show you an example:

9. anonymous

I have no idea, probably though. Good point, okay.

10. anonymous

Sorry about that, internet in the second star could be a bit iffy at times haha Getting the inverse of a function is easy enough in theory, even though it's not always so in practice. Thankfully, linear equations are always easy. So... $\large f(x) = 4x - 16$ First step and this is optional, but I always do it (in my head at least) to make things look nicer, and that's to replace f(x) with y $\large \color{red}{y} = 4x-16$

11. anonymous

Got it?

12. anonymous

Yes. And then you do it again but with x so it's x = 4y - 16, right?

13. anonymous

That's right :D But you're going to have to say that properly, though, and clearly (unlike that idiot who wrote that video game problem from last time ugh) So say that you will switch x and y. $\large \color{blue}x = 4\color{blue}y - 16$

14. anonymous

lol Then you add 16 to both sides?

15. anonymous

So it should look like... |dw:1441987136393:dw|

16. anonymous

@texaschic101 Can you help me please? The person who was helping me is having internet problems ._.

17. anonymous

I have a name, you know :P

18. anonymous

Well I don't know it :P

19. anonymous

It's Kurt haha Anyway, you did it correctly, just one more final touch ^^

20. anonymous

You replaced f(x) with y. Now we replace y. With... $\Large f^{-1}(x) = \frac{x+16}{4}$

21. anonymous

Hey... Are you still there?

22. anonymous

Yeah sorry. I accidentally closed the tab. Okay, that makes sense... Now how do I put it into the problem that they gave me?

23. anonymous

Just do the same, and use Pedro's bloody function :D

24. anonymous

Okay so... f(x) =4x - 3/2 y = 4x - 3 / 2 x = 4y - 3 / 2 then add 3 to each side?

25. anonymous

Nope, not quite. $\Large x = \frac{4y-3}2$ You kind of have to get rid of that 2 in the bottom, first. Try multiplying both sides by 2.

26. anonymous

So we would cancel out the 2 all together?

27. terenzreignz

Yup, while multiplying the left x with a 2. HAHA account back to normal... I feel more formal already (even though I'm not LOL)

28. terenzreignz

$\Large \color{red}2\cdot x = \frac{4y-3}2\cdot \color{blue}2$

29. anonymous

I'm lost .-. It's harder when it's already in a fraction.

30. terenzreignz

You're lost? I thought your name was Hayley :D HAHA Don't be afraid of fractions, they're just numbers trying to look tough ^^ In fact, multiplying the 2 get rid of the fraction bar: $\Large 2x = \frac{4y-3}{\cancel{2}}\cdot \cancel{2}$$\Large 2x = 4y - 3$

31. anonymous

Yeah yeah, whatever :P lol Okay... how do you ride of the 4 in the y? Don't we need a variable all by itself?

32. terenzreignz

Sshh... One at a time, Miss lost. First, your original idea. We add three to both sides to remove that 3. We couldn't do it earlier because, well, there was a denominator. But now there isn't. So... add the 3 and you get...?

33. anonymous

OH OH, I got it now!! So... |dw:1441989280403:dw|

34. terenzreignz

And the final touch $\Large f^{-1}(x) = \frac{2x + 3}4$ and Pedro can stick that up his... well, wherever he does his maths HAHA Well done! Amazing Grace!! HAHA You once... were lost... but now... you're... well, something Good job ^^

35. anonymous

Yay! Thank you so much. You are a life saver... well grade saver I guess ^.^

36. terenzreignz

No problem. ^_^ I am like super smart, after all... AHAHAHAHA or maybe just a little :)

37. anonymous

Or a lot :P

#### Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy