GRE Question of the Day (February 5)

If \({x^2 - y^2 = 1}\) and the average (arithmetic mean) of x and y is 4, what is the value of x - y ?

A. \({\frac{{1}}{{8}}}\)

B. \({\frac{{1}}{{4}}}\)

C. \({\frac{{1}}{{2}}}\)

D. \({2}\)

E. \({4}\)