\(x\propto y\) এবং \(y\propto z\) হলে, দেখাও যে \(\cfrac{x}{yz}+\cfrac{y}{zx}+\cfrac{z}{xy}\propto \cfrac{1}{x}+\cfrac{1}{y}+\cfrac{1}{z}\)
Madhyamik 2023
\(\because x∝y\)
\(\therefore x=ky\,\) [ \(k\) অশূন্য ভেদ ধ্রুবক ]
আবার, \(y\propto z\)
\(\therefore z\propto y\)
বা, \(z=my\,\) [ \(m\) অশূন্য ভেদ ধ্রুবক ]
এখন, \(\cfrac{\cfrac{x}{yz}+\cfrac{y}{zx}+\cfrac{z}{xy}}{ \cfrac{1}{x}+\cfrac{1}{y}+\cfrac{1}{z}}\)
\(=\cfrac{\cfrac{x^2+y^2+z^2}{xyz}}{ \cfrac{yz+zx+xy}{xyz}}\)
\(=\cfrac{x^2+y^2+z^2}{xy+yz+zx}\)
\(=\cfrac{k^2y^2+y^2+m^2y^2}{ky\cdot y+y\cdot my+my\cdot ky}\)
\(=\cfrac{y^2(k^2+1+m^2)}{y^2(k+m+mk)}\)
\(=\cfrac{k^2+m^2+1}{mk+k+m}=\) ধ্রুবক
\(\therefore \cfrac{x}{yz}+\cfrac{y}{zx}+\cfrac{z}{xy}\propto \cfrac{1}{x}+\cfrac{1}{y}+\cfrac{1}{z}\)[প্রমাণিত]