$$(\sqrt5+\sqrt{11})(\sqrt5-\sqrt{11})$$ is equal to:

Correct option is A

Given: 

​$$(\sqrt5+\sqrt{11})(\sqrt5-\sqrt{11})$$​
Concept Used:

​$$(a + b)(a - b) = a^2 - b^2$$ 

Solution: 

​$$(\sqrt5+\sqrt{11})(\sqrt5-\sqrt{11}) \\ \ \\ = (\sqrt5)^2 - (\sqrt{11})^2 \\ \ \\ = 5 - 11 \\ \ \\ = -6$$​​