If x^4 - 1/x^4=816√2, what is x?????

Answer 1

assuming the usual carelessness with parentheses,
(x^4-1)/x^4 = 816√2
1 - 1/x^4 = 816√2 - 1
1/x^4 = 2-816√2
x^4 = -(1+408√2)/665854