I am self-studying Rational Points over Elliptic Curves (Silverman & Tate) and am working on the following question:
$1.17$ Let $C$ be a cubic curve in the projective plane given by the homogeneous equation $$Y^2Z = X^3 + aX^2Z + bXZ^2 + cZ^3$$ Verify that the point $[0,1,0]$ at infinity is a non-singular point of $C$.
I am hoping to get some feedback on my proof, and if it is wrong, could someone point me in the right direction or give a correct proof? Here's what I have:
Let $F(X, Y, Z) = X^3 + aX^2Z + bXZ^2 + cZ^3 - Y^2Z$. Then we have that \begin{align} F_X &= 3X^2 + 2aXZ + bZ^2 \\ F_Y &= 2YZ \\ F_ Z &= aX^2 + 2bXZ + 3cZ^2 - Y^2. \end{align} So at the point $[0,1,0]$, we have that \begin{align} F_X (0) &= 0 \\ F_Y (0) &= 0 \\ F_Z (0) &= 1, \end{align} so the point is a non-singular point.
Is this all I have to do?
You have misinterprted the question. You are not being asked to hunt for singular points on the curve. You are required to show that the particular point (0:1:0) is a non-singular point, so what is required is to show that, regardless of what values are taken by the parameters $a,b,c$, all three partial derivatives cannot be 0 at (0:1:0).