The points on the curve $9y^2=x^3$ where normal to the curve makes equal intercepts with the axes is/are :
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → $\left(4, \frac{8}{3}\right),\left(4, \frac{-8}{3}\right)$
$9y^2=x^3$ ...(1)
differentiating wrt (x)
$18y\frac{dy}{dx}=3x^2$
so $\frac{dy}{dx}=\frac{x^2}{6y}$
slope of normal → $-\frac{dy}{dx}=(-\frac{x^2}{6y})^{-1}$
as it makes equal intersepts
$-\frac{x^2}{6y}=-1⇒6y=x^2$
or $y=\frac{x^2}{6}$
from (1) $9×\frac{x^4}{36}=x^3$
so $x=4$
from (1) $9y^2=4^3$
$y^2=\frac{64}{9}$
$y=±\frac{8}{3}$
Points $\left(4, ±\frac{8}{3}\right)$