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
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DT
2
25 tháng 3 2020
a) \(\frac{2}{21}+\frac{1}{28}=\frac{8}{84}+\frac{3}{84}=\frac{11}{84}\)
b) \(2+\frac{-3}{4}=\frac{8}{4}+\frac{-3}{4}=\frac{5}{4}\)
c) \(\frac{13}{5}+\frac{5}{3}=\frac{39}{15}+\frac{25}{15}=\frac{64}{15}\)
DT
0
DT
0
11 tháng 6 2019
\(a,\frac{3}{17}+\frac{-5}{13}+\frac{-18}{35}+\frac{14}{17}+\frac{17}{-35}\)
=\(-\frac{5}{13}+\left(\frac{3}{17}+\frac{14}{17}\right)+\left(\frac{-18}{35}+\frac{-17}{35}\right)\)
= \(-\frac{5}{13}+1+\left(-1\right)\)
=\(-\frac{5}{13}\)
\(b,\frac{-3}{8}.\frac{1}{6}+\frac{3}{-8}.\frac{5}{6}+\frac{-10}{6}\)
=\(\frac{-3}{8}.\left(\frac{1}{6}+\frac{5}{6}\right)+\frac{-10}{6}\)
=\(\frac{-3}{8}.1+\frac{-10}{6}\)
=\(-\frac{49}{24}\)
\(c,\frac{-4}{11}.\frac{5}{15}.\frac{11}{-4}\)
=\(\left(\frac{-4}{11}.\frac{11}{-4}\right).\frac{1}{3}\)
=\(1.\frac{1}{3}=\frac{1}{3}\)
\(d,\frac{13}{8}+\frac{1}{8}:\left(0,75-\frac{1}{2}\right)-25\%.\frac{1}{2}\)
=\(\frac{13}{8}+\frac{1}{8}:\left(\frac{3}{4}-\frac{1}{2}\right)-\frac{1}{4}.\frac{1}{2}\)
=\(\frac{13}{8}+\frac{1}{8}:\frac{1}{4}-\frac{1}{8}\)
=\(\frac{13}{8}+\frac{1}{2}+\frac{-1}{8}\)
=\(\left(\frac{13}{8}+\frac{-1}{8}\right)+\frac{1}{2}\)
=\(\frac{3}{2}+\frac{1}{2}=2\)
\(e,\frac{-1}{2^2}-\left(-2\right)^2-5\)
=\(\frac{-1}{4}-4-5\)
=\(-\frac{37}{4}\)
\(f,\frac{121}{3}-\frac{5}{7}:\left(24-\frac{23}{57}\right)\)
=\(\frac{121}{3}-\frac{5}{7}:\frac{1345}{57}\)
=\(\frac{121}{3}-\frac{57}{1883}\)
\(\approx40,4\)
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) \(\frac{13}{5}+\frac{5}{3}=\frac{13.3}{5.3}+\frac{5.5}{3.5}=\frac{39}{15}+\frac{25}{15}=\frac{39+25}{15}=\frac{64}{15}.\)
Chúc bạn học tốt!
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)\({\\{13} \over 5}\)+\({\\{5} \over 3}\)= \({\\{39} \over 15}\)+\({\\{25} \over 15}\)=\({\\{64} \over 15}\)
Học tốt