URGENT HELP WITH some problems. :x

Okay it starts with how to use algebraic tests to check for symmetry with respect to both axes and the origin.

13. y = -4x+1

14. y= 5x-6

15. y=5-x^squared

16.y=x^squared - 10

17. y=x cubed + 3

18. y= -6 -x cubed

19. y = square root of x +5

20. y=|x| +9

And..

I know theres this formula for this its (x-h) squared + (y-k) squared = r squared but

How to find the center of a radius of a circle when they give u just this

21. x squared + y squared = 9

22. x squared + y squared = 4

23. (x+2)squared + y squared = 16

24.x squared + (y-8)squared = 81

25. (x - 1/2) squared + (y + 1)squared = 36

26. (x+4) squared + (y - 3/2)squared = 100

Whoever answers them all first gets thanks IF they helped me understand how to do them correctly

much love

-THANKS