this is normal math sqrt√(x)^2,
      test value: 4^2 = 16, next root return 4
                       -8^2= 64,next root return 8

how to bitcoin Publickey x and y use to  sqrt example: √(x,y)^2
how to calculate sqrt for bitcoin publickey teach me please

example1:x,y
px: e493dbf1c10d80f3581e4904930b1404cc6c13900ee0758474fa94abe8c4cd13   py: 51ed993ea0d455b75642e2098ea51448d967ae33bfbdfe40cfe97bdc47739922 #privatekey 4
px: 421f5fc9a21065445c96fdb91c0c1e2f2431741c72713b4b99ddcb316f31e9fc   py: 2b90f16d11dabdb616f6db7e225d1e14743034b37b223115db20717ad1cd6781 #privatekey 4^2 = 16
ans
px: e493dbf1c10d80f3581e4904930b1404cc6c13900ee0758474fa94abe8c4cd13   py: 51ed993ea0d455b75642e2098ea51448d967ae33bfbdfe40cfe97bdc47739922 #privatekey √16 = 4

example2:
px: 2f01e5e15cca351daff3843fb70f3c2f0a1bdd05e5af888a67784ef3e10a2a01   py: a3b25758beac66b6d6c2f7d5ecd2ec4b3d1dec2945a489e84a25d3479342132b # -8
px: ed3bace23c5e17652e174c835fb72bf53ee306b3406a26890221b4cef7500f88   py: e57a6f571288ccffdcda5e8a7a1f87bf97bd17be084895d0fce17ad5e335286e # -8^ = 64
ans
px: 2f01e5e15cca351daff3843fb70f3c2f0a1bdd05e5af888a67784ef3e10a2a01   py: 5c4da8a741539949293d082a132d13b4c2e213d6ba5b7617b5da2cb76cbde904 # √64 = 8

how does work explain. do u understad my problem ,i speak little english