## shelby1290 one year ago Determine the radius and the center of the following circles. Round to the nearest tenth. a) x^2 + y^2 = 81 radius= ? center=? b) x^2 + y^2 = 1 radius= ? centre= ?

1. jim_thompson5910

|dw:1434503664766:dw|

2. jim_thompson5910

the original x and y can be written as (x-0) and (y-0) |dw:1434503681112:dw|

3. jim_thompson5910

81 is the same as 9^2 |dw:1434503731384:dw|

4. jim_thompson5910

|dw:1434503759321:dw|

5. jim_thompson5910

compare that to \(\Large (x-h)^2 + (y-k)^2 = r^2\) |dw:1434503785488:dw|

6. jim_thompson5910

|dw:1434503824871:dw|

7. jim_thompson5910

Hopefully all that makes sense?

8. shelby1290

@jim_thompson5910 yea it makes sense but which one is the centre?

9. jim_thompson5910

(h,k) is the center r is the radius

10. jim_thompson5910

|dw:1434503924630:dw|

11. shelby1290

alright

12. shelby1290

and for part b you can't square 1 so what do you do ?

13. jim_thompson5910

yes you can, 1 = 1^2

14. shelby1290

ohhh yea

15. shelby1290

i'm going to try part by myself and then you can check it over for me

16. jim_thompson5910

sure

17. shelby1290

|dw:1434504154480:dw|

18. shelby1290

|dw:1434504263508:dw|

19. shelby1290

@jim_thompson5910 ^

20. jim_thompson5910

very nice you have the correct steps, center and radius

21. shelby1290

thanks for the help!

22. jim_thompson5910

you're welcome