## anonymous 5 years ago Need help with the washer method: x=1-y^2, x=2+y^2, =-1, y=1

1. anonymous

*should be y=-1

2. anonymous

x=-1 , y=-1?

3. anonymous

try out this website. http://tutorial.math.lamar.edu/Classes/CalcII/CalcII.aspx

4. anonymous

So you have two function. Find out which one is to the right.

5. anonymous

x=2+y^2 would be to the right, right?

6. anonymous

hold on

7. anonymous

are your functions correct, they don't seem to intersect

8. anonymous

yep, they are correct. I also forgot to put its revolved around the y-axis

9. anonymous

because the functions don't even touch each other

10. anonymous

That's really strange, I wonder if the text made an error

11. anonymous

For washer method, we are supposed to take revolution of intersection between two functions

12. anonymous

That much I understand, maybe I should try converting the equation to xs and see what happens.

13. anonymous

If we change second function to x=-2+y^2 we can solve it, do you wanna

14. anonymous

sure : )

15. anonymous

We will rotate around x=-3

16. anonymous

Here come the integral $\pi \int\limits_{?}^{?}((-y^2-1)-(y^2-2)+1)^2-1$

17. anonymous

dy

18. anonymous

did you get it, mathrocks?

19. anonymous

Ok, this is starting to make some sense.

20. anonymous

you have to find points of intersection though

21. anonymous

Never memorize any formula for disc,shell, washer method

22. anonymous

I can find the intersection points with no problem. It's just setting up the washer equation that sometimes trips me up. Thanks for your help, I appreciate it.

23. anonymous

just know that when you are doing this type of problem, you are adding up circle

24. anonymous

If I helped you in somehow, can you fan me

25. anonymous

I'll remember that and will practice drawing the actual graphs. And the fan request has been done. : )