Let $S$ be the focus of the parabola $y^2=4 a x$ and $\mathrm{PQ}$ be a focal chord such that…
Let $S$ be the focus of the parabola $y^2=4 a x$ and $\mathrm{PQ}$ be a focal chord such that $\mathrm{SP}=\alpha$ and $\mathrm{SQ}=\alpha^{\prime}$. Then $\frac{1}{\alpha}+\frac{1}{\alpha^{\prime}}=$