I need help with simplifying!

sqrt(2*sqrt(8^2 + 15^2) + sqrt(9^2 + 40^2))

= sqrt(2*17 + 44)

= sqrt(78)

Let's see,

$\sqrt{2\sqrt{8^2+15^2}+\sqrt{9^2+40^2}}\\ =\sqrt{2\sqrt{289}+\sqrt{1681}}\\ =\sqrt{2*17+41}\\ =\sqrt{34+41}\\ =\sqrt{75}\\ =5\sqrt{3}\\$

Guest just made a careless error that you should have found for yourself !

Thanks Guest.