Question

15) Calcule o valor das expressões abaixo (para somar ou subtrair é preciso tirar o mmc) por favor! me ajudem
$\frac{2}{3} + \frac{7}{6}$
$3 \frac{1}{2} + \frac{4}{5}$
$\frac{5}{4} - \frac{4}{5}$
$3 - \frac{2}{5}$​

Answer 1

$\Large\boxed{\begin{array}{l}\underline{\rm Soma\,de\,frac_{\!\!,}\tilde oes}\\\underline{\rm pelo\,m\acute etodo\,da\,borboleta}\\\huge\boxed{\boxed{\boxed{\boxed{\sf\dfrac{a}{b}+\dfrac{c}{d}=\dfrac{a\cdot d+b \cdot c}{b\cdot d}}}}}\end{array}}$

$\boxed{\begin{array}{l}\underline{\rm Convers\tilde ao\,da\,frac_{\!\!,}\tilde ao\,mista}\\\underline{\rm para\,frac_{\!\!,}\tilde ao\,impr\acute opria}\\\sf quociente\dfrac{resto}{divisor}=\dfrac{quociente\cdot divisor+resto}{divisor}\end{array}}$

$\Large\boxed{\begin{array}{l}\sf\dfrac{2}{3}+\dfrac{7}{6}=\dfrac{2\cdot6+3\cdot7}{3\cdot6}\\\\\sf \dfrac{2}{3}+\dfrac{7}{6}=\dfrac{12+21}{18}=\dfrac{33\div3}{18\div3}=\dfrac{11}{6}\end{array}}$

$\Large\boxed{\begin{array}{l}\sf 3\,\dfrac{1}{2}=\dfrac{3\cdot2+1}{2}=\dfrac{6+1}{2}=\dfrac{7}{2}\\\\\sf3\,\dfrac{1}{2}+\dfrac{4}{5}=\dfrac{7}{2}+\dfrac{4}{5}\\\\\sf \dfrac{7}{2}+\dfrac{4}{5}=\dfrac{7\cdot5+2\cdot4}{2\cdot5}\\\\\sf\dfrac{7}{2}+\dfrac{4}{5}=\dfrac{35+8}{10}=\dfrac{43}{10}\end{array}}$

$\Large\boxed{\begin{array}{l}\sf\dfrac{5}{4}-\dfrac{4}{5}=\dfrac{5\cdot5-4\cdot4}{4\cdot5}\\\\\sf\dfrac{5}{4}-\dfrac{4}{5}=\dfrac{25-16}{20}\\\\\sf\dfrac{5}{4}-\dfrac{4}{5}=\dfrac{9}{20}\end{array}}$

$\Large\boxed{\begin{array}{l}\sf 3-\dfrac{2}{5}=\dfrac{3}{1}-\dfrac{2}{5}\\\\\sf\dfrac{3}{1}-\dfrac{2}{5}=\dfrac{3\cdot5-1\cdot2}{1\cdot5}\\\\\sf\dfrac{3}{1}-\dfrac{2}{5}=\dfrac{15-2}{5}\\\\\sf\dfrac{3}{1}-\dfrac{2}{5}=\dfrac{13}{5}\end{array}}$