Resposta:
Substituir as letras pelos valores dados
a)
[tex]{a^2-2a\over\sqrt{a} }=\\ \\ {4^2-2.(4)\over\sqrt{4} }=\\ \\{ 16-8\over2}=\\ \\ {8\over2}=4[/tex]
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b)
[tex]m^2-2mn+n^2=\\ \\ (-1)^2-2(-1)({1\over4})+({1\over4})^2=\\ \\ +1+{2\over4}+{1\over16}=\\ \\ mmc(4,16)=16\\ \\ {16+8+1\over16}={25\over16}[/tex]
