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

It is in the form of $(a-b)(a+b)=a^2-b^2=11-7=4$

Hence, the correct answer is option (b