How do I solve this?

Question

Determine the equation of the given conic in XY-coordinates when the coordinate axes are rotated through the indicated angle.

xy = x + y, 𝜑 = 𝜋/4

Answer 1

x = x' cos θ - y' sin θ

y = x' sin θ + y' cos θ

Substitute π/4 then substitute into

x - xy + y = 0