Practicing Success
A particle moves along the curve $6y=x^3+2$, the point(s) on the curve at which y coordinate is/are changing 8 times as fast as x coordinate are : |
$(4, 11)$ and $(-4, \frac{-31}{3})$ $(-4, \frac{-31}{3})$ and (-4, 11) (4, -4) $(11, \frac{-31}{3})$ |
$(4, 11)$ and $(-4, \frac{-31}{3})$ |
The correct answer is Option (1) → $(4, 11)$ and $(-4, \frac{-31}{3})$ $6y=x^3+2$ so $6\frac{dy}{dx}=3x^2⇒\frac{dy}{dx}=\frac{x^2}{2}$ given y coordinate changes 8 times as fast as x $⇒\frac{dy}{dx}=8⇒\frac{x^2}{2}=8⇒x=±4$ so $6y=±64+2$ $y=\frac{±64+2}{6}$ so $(x,y)=(4, 11)$ or $(-4, \frac{-31}{3})$ |