Algebra II Honors Homework Help

1. Dec 9, 2011

darshanpatel

The inverse of f(x)= k(-x^3 -4x -9) is a function and f^-1(7)=1. What is the value of k?

Work is a picture: http://tinypic.com/view.php?pic=29xj4i8&s=5

Mod note: Too large picture deleted

Last edited by a moderator: Dec 9, 2011
2. Dec 9, 2011

SammyS

Staff Emeritus
Hello darshanpatel. Welcome to PF.

Here's a hint: If $\displaystyle f^{-1}(7)=1\,,$ then what is $\displaystyle f(1)\,?$

Note: When a moderator of these forums sees the size of that image, he/she will likely delete it.

3. Dec 9, 2011

darshanpatel

The y is from exchanging the x and y's to get the inverse, also can you please help me and not hint lol.

4. Dec 9, 2011

SammyS

Staff Emeritus
LOL indeed!

Read the rules of these Forums.

By the way: The hint I gave should lead you directly to the solution.

5. Dec 9, 2011

Staff: Mentor

Picture copied.

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6. Dec 9, 2011

SammyS

Staff Emeritus
Thanks Evo !!!

7. Dec 9, 2011

darshanpatel

I dont understand the hint... Do I plug it directly in or something?

Also Another PF mod or something said it was ok...

8. Dec 9, 2011

SammyS

Staff Emeritus

9. Dec 9, 2011

darshanpatel

So I plug 1 into x variables and make whole equation = to 7?

10. Dec 9, 2011

SammyS

Staff Emeritus
Yes. Then solve for k.

11. Dec 9, 2011

darshanpatel

Thank you, you are really smart. :)

12. Dec 9, 2011

Staff: Mentor

If it is much larger than 800 x 600 pixels, the moderators will likely delete it.

13. Dec 10, 2011

darshanpatel

ok, thanks...