Question 1016335
*[tex \large (\sqrt{a} + \sqrt{b})^2 = a + b + 2 \sqrt{ab}] by expanding/using FOIL.


*[tex \large (-\sqrt{a} - \sqrt{b})^2 = (-(\sqrt{a} + \sqrt{b}))^2 = a + b + 2 \sqrt{ab}] (same as the first one)


Note that *[tex \large \sqrt{84} = 2 \sqrt{21}]. Setting a = 7, b = 3 gives *[tex \large (\sqrt{7} + \sqrt{3})^2 = 10 + \sqrt{84}].