Let \(s\) be the side of the square and \(d\) be the diagonal.
Thus; \(d = s + 5\)
\(d^2 = s^2 +s^2 \)
\((s + 5)^2 = s^2 +s^2\)
\(s^2 +10s + 25 = 2s^2 \)
\(s^2 - 10s -25 = 0\)
\(d = \dfrac{10+\sqrt{100+100}}{2}\)
\(d = 5 +5\sqrt{2}\)ANSWER
