(1)400=20^2 1936=44^2 5776=76^2
(2)20=25-5=5^2-5
44=49-5=7^2-5
76=81-5=9^2-5
(3)(n-3)(n-1)(n+1)(n+3)+16=n^4-10n^2+25=(n^2-5)^2
(1)400=20^2 1936=44^2 5776=76^2
(2)20=25-5=5^2-5
44=49-5=7^2-5
76=81-5=9^2-5
(3)(n-3)(n-1)(n+1)(n+3)+16=n^4-10n^2+25=(n^2-5)^2