Simplify the following expressions:
 
(i) \((4+\sqrt{7})(3+\sqrt{7})=\) \(+\)  i \(+\) i \(+\)
 
(ii) \((7+\sqrt{7})(7-\sqrt{7})=\)
 
(iii) \((\sqrt{3}+\sqrt{7})^2=\) \(+2\) i \(+\) .
 
(iv) \((\sqrt{5}+\sqrt{7})\)\((\sqrt{5}-\sqrt{7}) =\)