On this link, in the convex lens second method to calculate focal length. I did not understand how the graph of 1/u and 1/v can give 1/f as the intercept? Could someone please explain?
$\frac1u+\frac1v=\frac1f$, where $f$ is some constant property of the lens. Let $y=1/u$, and $x=1/v$. Then $y=1/f − x$, which is the equation of a straight line, gradient $-1$ and $y$-intercept $1/f$. Setting $y=0$, we can get the $x$-intercept which it turns out is also $1/f$.