Question

 

a, 2 phần 21 + 1 phần 28 

b, 2 + -3 phần  4 

c, 13 phần 5 + 5 phần 3 

làm ơn giúp mk đi huhuhuhuhu

Answer 1

a) \(\frac{2}{21}+\frac{1}{28}=\frac{2.4}{21.4}+\frac{1.3}{28.3}=\frac{8}{84}+\frac{3}{84}=\frac{8+3}{84}=\frac{11}{84}.\)

b) \(2+\left(-\frac{3}{4}\right)=\frac{2}{1}+\left(-\frac{3}{4}\right)=\frac{2.4}{1.4}+\left(-\frac{3}{4}\right)=\frac{8}{4}+\left(-\frac{3}{4}\right)=\frac{8+\left(-3\right)}{4}=\frac{5}{4}.\)

c) \(\frac{13}{5}+\frac{5}{3}=\frac{13.3}{5.3}+\frac{5.5}{3.5}=\frac{39}{15}+\frac{25}{15}=\frac{39+25}{15}=\frac{64}{15}.\)

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Answer 2

a)\({\\{2} \over 21}\)+\({\\{1} \over 28}\)= \({\\{8} \over 84}\)+\({\\{3} \over 84}\)= \({\\{11} \over 84}\)

b) 2+\({\\{3} \over 4}\)= \({\\{8} \over 4}\)+\({\\{3} \over 4}\)=\({\\{11} \over 4}\)

c)\({\\{13} \over 5}\)+\({\\{5} \over 3}\)= \({\\{39} \over 15}\)+\({\\{25} \over 15}\)=\({\\{64} \over 15}\)

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