Answer:
The combined law is:
[tex]\dfrac{P_1V_1}{T_1}=\dfrac{P_2V_2}{T_2}[/tex]
See the derivation below.
Explanation:
1. Boyle's law:
[tex]PV=constant\\\\P_1V_1=P_2V_2[/tex]
2. Charles' law:
[tex]\dfrac{V}{T}=constant\\\\\\\dfrac{V_1}{T_1}=\dfrac{V_2}{T_2}[/tex]
3. Gay-Lussac’s law
[tex]\dfrac{P}{T}=constant\\\\\\\dfrac{P_1}{T_1}=\dfrac{P_2}{T_2}[/tex]
4. Summary:
Mulitply PV by V/T and P/T
[tex]PV\times \dfrac{V}{T}\times \dfrac{P}{T}=K\times K'\times K''\\\\\\\dfrac{P^2V^2}{T^2}=constant\\\\\\\sqrt{\dfrac{P^2V^2}{T^2}}=\sqrt{constant}\\\\\\\dfrac{PV}{T}=constant[/tex]
Thus:
[tex]\dfrac{P_1V_1}{T_1}=\dfrac{P_2V_2}{T_2}[/tex]
Which is the combined law.