Answer:
see attached
Explanation:
The legs of the right triangles are drawn along the grid lines. You can count the grid lines to see how long they are. Use the given formula to find the square of the hypotenuse, then take the square root. The hypotenuse of each triangle is the straight-line distance between its end points.
It should be no surprise that 3^2 +4^2 is more than 3^2 +3^2, so the length from B to C will be longer than from A to C.
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Additional comment
3√2 ≈ 4.24