Find the points on the curve $y^{2}=2 x^{3}$ at which the slope of the tangent is 3 .
Let $\left(x_{1}, y_{1}\right)$ be the required point.
Given:
$y^{2}=2 x^{3}$
Since $\left(x_{1} y_{1}\right)$ lies on a curve, $y_{1}^{2}=2 x_{1}{ }^{3}$ .....(i)
$\Rightarrow 2 y \frac{d y}{d x}=6 x^{2}$
$\Rightarrow \frac{d y}{d x}=\frac{6 x^{2}}{2 y}=\frac{3 x^{2}}{y}$
Slope of the tangent at $(x, y)=\frac{3 x_{1}{ }^{2}}{y_{1}}$
Slope of the tangent $=3$ [Given]
$\therefore \frac{3 x_{1}^{2}}{y_{1}}=3$ ....(2)
$\Rightarrow y_{1}=x_{1}^{2}$
On substituting the value of $y_{1}$ in eq. (1), we get
$x_{1}^{4}=2 x_{1}^{3}$
$\Rightarrow x_{1}^{3}\left(x_{1}-2\right)=0$
$\Rightarrow x_{1}=0,2$
Case 1
When $x_{1}=0, y_{1}=x^{2}=0$. Thus, we get the point $(0,0)$. But, it does not satisfy eq. (2).
So, we can ignore $(0,0)$.
Case 2
When $x_{1}=2, y_{1}=x_{1}^{2}=4$. Thus, we get the point $(2,4)$.