A point moves along the ellipse and remains in the first quadrant

MATHEMATICS · Subjective · AP · Calculus AB · Contextual Applications of Differentiation · Contextual Applications of Differentiation

Problem

A point moves along the ellipse

x^{2}+4y^{2}=25

and remains in the first quadrant. At an instant when

dx/dt

is negative, must

dy/dt

be positive or negative? Briefly justify your answer.