Step-by-step explanation:
We know that
[tex]P_1V_1^k = P_2V_2^k[/tex]
or
[tex]\left(\dfrac{P_1}{P_2} \right) = \left(\dfrac{V_2}{V_1} \right)^k[/tex] (1)
and
[tex]\dfrac{P_1V_1}{T_1} = \dfrac{P_2V_2}{T_2}[/tex] (2)
Let's move the P and V variables in Eqn(2) to the right side:
[tex]\dfrac{T_1}{T_2} = \left(\dfrac{P_1}{P_2} \right)\left(\dfrac{V_1}{V_2} \right)[/tex] (3)
Substitute Eqn(1) into Eqn(3):
[tex]\dfrac{T_1}{T_2} = \left(\dfrac{V_2}{V_1} \right)^k \left(\dfrac{V_1}{V_2} \right) [/tex]
[tex]\:\:\:\:\:\:\:= \left(\dfrac{V_2}{V_1} \right)^{k-1}[/tex]