Question 237281
Use the Pythagorean Theorem: a^2 + b^2 = c^2


(AC)^2 + (BC)^2 = (AB)^2

5^2 + 6^2 = (AB)^2

25 + 36 = (AB)^2

61 = (AB)^2

sqrt{61} = AB

By the way, sqrt = square root for short.