Answer:
√77
Step-by-step explanation:
The Pythagorean theorem is used for this. It tells you the sum of the squares of the leg lengths is the square of the hypotenuse.
If x represents the unknown side, then ...
2² +x² = 9²
x² = 81 -4 = 77 . . . . subtract 4
x = √77 . . . . . . . . . . take the square root
The exact length of the third side is √77.
