What is the line drawn on the diagram called?

Which expression is equivalent to 4 square root 6 divided by 3 root 2

Simplify 4 square root of 2 end root plus 7 square root of 2 end root minus 3 square root of 2 . (1 point) 2 square root of 8 8 square root of 2 8 square root of 6 6 square root of 8

Can someone check if i did this correct. it’s number 4 if you’re wondering.