Chứng minh rằng:

a) \({\left( {1 - \sqrt 2 } \right)^2} = {1^2} - 2\sqrt 2 + {\left( {\sqrt 2 } \right)^2}\)

\( = 1 - 2\sqrt 2 + 2 = 3 - 2\sqrt 2 \).

b) \[{\left( {\sqrt 3 + \sqrt 2 } \right)^2} = {\left( {\sqrt 3 } \right)^2} + 2\sqrt 3 .\sqrt 2 + {\left( {\sqrt 2 } \right)^2}\]

\[ = 3 + 2\sqrt 6 + 2 = 5 + 2\sqrt 6 \].