Thank you for reporting, we will resolve it shortly
Q.
From a spherical mirror, the graph of $1/v$ vs $1/u$ is
Ray Optics and Optical Instruments
Solution:
$ \frac{1}{v}+\frac{1}{u}=\frac{1}{f} .$ If $y=\frac{1}{v}$ and $x=\frac{1}{u} \Rightarrow y+x=c$
where $c=\frac{1}{f}$ is a straight graph with a -ve slope.