The point on the curve $9 y^{2}=x^{3}$, where the normal to the curve makes equal intercepts with the axes is
A. $\left(4, \pm \frac{8}{3}\right)$
B. $\left(-4, \frac{8}{3}\right)$
C. $\left(-4,-\frac{8}{3}\right)$
D. $\left(\frac{8}{3}, 4\right)$
Given curve $9 y^{2}=x^{3} \ldots$ (1)
Differentiate w.r.t. $x$,
$18 y \frac{d y}{d x}=3 x^{2}$
$\Rightarrow \frac{d y}{d x}=\frac{x^{2}}{6 y}$
Equation of normal:
$\left(\mathrm{y}-\mathrm{y}_{1}\right)=\frac{-1}{\text { Slope of tangent }}\left(\mathrm{x}-\mathrm{x}_{1}\right)$
$\because$ it makes equal intercepts with the axes
$\therefore$ slope of the normal $=\pm 1$
$\Rightarrow x^{2}=\pm 6 y$
Squaring both the sides,
$x^{4}=\pm 36 y^{2}$
From (1),
$x=0,4$
and $y=0, \pm \frac{8}{3}$
But the line making equal intercept cannot pass through origin.
So, the required points are $\left(4, \pm \frac{8}{3}\right)$.