The slope of the tangent line to a curve at any point (x, y) on the curve is x/y. What is the equation of the curve if (4, 1) is a point on the curve?
x2 − y2 = 15
x2 + y2 = 15
x + y = 15
xy = 15
x2 − y2 = 15
x2 + y2 = 15
x + y = 15
xy = 15