A² + b² = c². Make a triangle with the points on a grid. One leg is 7 units and the other is 1 unit. 7² is 49 and 1² is 1. 49 + 1 = 50 √50 ≈ 7.071. Hope this helps!
No, it is not a function. Since all the lines have been drawn in the grid line do not have any connection between them even a point in common. I hope this has been useful for you.