Respostas

2014-07-10T22:16:34-03:00
Olá Duda, tire o MMC das frações:

3+ \dfrac{1}{2}\\\\
3= \dfrac{6}{2}~ent\~ao,~podemos~somar,~ pois~os~denominadores~s\~ao~iguais:\\\\
 \dfrac{6}{2}+ \dfrac{1}{2}~\to~\boxed{\dfrac{7}{2}}

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3- \dfrac{1}{2}~\to~ \dfrac{6}{2}- \dfrac{1}{2}~\to~\boxed{ \dfrac{5}{2}}

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 \dfrac{1}{2}- \dfrac{2}{5}\\\\
MMC(2,5)=10\\\\
 \dfrac{5*1-2*2}{10}~\to~ \dfrac{5-4}{10} ~\to~ \boxed{\dfrac{1}{10}}

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 \dfrac{7}{5}+\dfrac{3}{4}\\\\
MMC(4,5)=20\\\\
 \dfrac{4*7+5*3}{20}~\to~ \dfrac{28+15}{20}~\to~ \boxed{\dfrac{43}{20}}

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 \dfrac{7}{5}- \dfrac{3}{4}\\\\
MMC(4,5)=20\\\\
 \dfrac{4*7-5*3}{20}~\to~ \dfrac{28-15}{20}~\to~ \boxed{\dfrac{13}{20}}

Espero ter ajudado e tenha ótimos estudos =))
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