I need help understanding the derivation of this 'Absolute Scale of Temperature'

[Shauryafrom2006]

TL;DR Summary

I can't figure out the derivation of this formula.

It is from [ Class 11th] SL Arora, pg no. 11.3, the heading is [11.7] Absolute Scale of Temperature.

 

[willem2]

This is just Charles law (V/T is onstant at constant pressure), with T expressed in degrees Celsius, so you get (T+273.15) in the expression, instead of t

 

[Shauryafrom2006]

Oh... I see, I get it now :)