I don't know how to answer this question given in a test recently and I thought someone might be able to help.
Bob adds a number, that is larger than 1, to its reciprocal. His answer is 4. Find Bob's number in the form a (add or subtract) square root of b
x + 1/x = 4
x^2 - 4x + 1 = 0
x = (4±√12)/2 = 2±√3
2-√3 < 1 so
x = 2+√3
check: 1/(2+√3) = 2-√3
so 2+√3 + 2-√3 = 4