1Explanation for your answer.
1. Langmuir Equation assumes that adsorption is monolayer. But, monolayer formation is possible only under low pressure condition. Under high pressure condition the assumption breaks down as gas molecules attract more and more molecules towards each other. BET theory proposed by Brunauer, Emmett and Teller explained more realistic multilayer adsorption process.
2. Langmuir Equation assumed that molecules do not interact with each other. This is impossible as weak force of attraction exists even between molecules of same type.
3. A dynamic equilibrium exists between the adsorbed molecules and the free gas molecules.
4. We consider Langmuir Equation 
At low pressure value of KP<<1. Therefore,
The above equation shows linear variation between extent of adsorption of gas and pressure.
At high pressure value of KP>>1
The extent of adsorption, θ is independent of pressure at high pressure conditions. The reaction at this stage becomes zero order
Combining the results of equation (4) and (5), we can conclude that
Equation (3) is in agreement with Freundlich adsorption equation.
We can say that Freundlich adsorption equation is a special case of Langmuir equation.
