Apparent magnitude isn’t the actual brightness, it’s what the brightness appears to be from earth, absolute brightness is the actual brightness an example is our sun it appears bright on earth but in space it is so much more brighter
Square root are the same 2 numbers multiplied.
Ex: 8*8=64 (Square root is 8)
9*9=81 (Square root is 9)
2.2360679775*2.2360679775=5
Answer=2.2360679775
So 15-7 is 8
Here are some things I did:
10-2 or 28-20