Mathematics

Problem

A point moves along the ellipse

4x^{2}+y^{2}=20

. At an instant when the point is in the first quadrant (

x>0,\,y>0

) its

x

–coordinate is decreasing at a rate of

3\text{ cm/s}

. Which statement about the instantaneous rate of change of the

y

–coordinate is true? a)

\dfrac{dy}{dt}=0

\dfrac{dy}{dt}

is negative c)

\dfrac{dy}{dt}

is positive d) The sign of

\dfrac{dy}{dt}

cannot be determined from the given information