Question

Which of the following is the value of $(\sqrt{11}-\sqrt{7})(\sqrt{11}+\sqrt{7})$

• A. $-4$
• B. $4$
• C. $\sqrt{11}$
• D. $\sqrt{7}$

Answer 1

The correct option is B $4$

$(a-b)(a+b)=a^2-b^2$

Similarly,

$(\sqrt{11}-\sqrt{7})(\sqrt{11}+\sqrt{7})=11-7=4$

So, $B$ is correct.