Resposta:

[tex]a) d = l \sqrt{2} \\ d = 3 \sqrt{2} \\ [/tex]

[tex]b)d = \sqrt{a { }^{2} + b {}^{2} } \\ d = \sqrt{2 {}^{2} + 4 {}^{2} } \\ d = \sqrt{4 + 16 \\ } \\ d = \sqrt{20} [/tex]