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Tk mình đi mọi người mình bị âm nè!
ai tk mình mình tk lại cho!!!
15 /17=17/17-2/17
3/5=5/5-2/5
Vì 17/17=5/5 mà 2/17<2/5 =>15/17>3/5
(vì phần bù càng lớn thì phân số càng bé)
\(a,MSC:170\\ \dfrac{7}{10}=\dfrac{7.17}{17.10}=\dfrac{119}{170}\\ \dfrac{-5}{15}=-\dfrac{1}{5}=\dfrac{1.34}{5.34}=\dfrac{34}{170}\\ \dfrac{3}{17}=\dfrac{3.10}{17.10}=\dfrac{30}{17}\\ b,MSC:525\\ \dfrac{-4}{-75}=\dfrac{4}{75}=\dfrac{4.7}{75.7}=\dfrac{28}{525}\\ \dfrac{-3}{5}=\dfrac{-3.105}{5.105}=\dfrac{-315}{525}\\ \dfrac{8}{35}=\dfrac{8.15}{35.15}=\dfrac{120}{525}\)
BÀI 1:
a) \(\frac{4}{5}+\frac{3}{8}+\frac{1}{4}\)
\(=\frac{32}{40}+\frac{15}{40}+\frac{10}{40}\)
\(=\frac{32+15+10}{40}\)\(=\frac{57}{40}\)
b) \(\frac{5}{9}+\frac{2}{3}+\frac{1}{2}\)
\(=\frac{10}{18}+\frac{12}{18}+\frac{9}{18}\)
\(=\frac{10+12+9}{18}=\frac{31}{18}\)
\(\frac{1}{3};\frac{2}{15};\frac{4}{45}\)
Ta có : Mẫu số chung là 45 vì \(45\) \(⋮3;15\)
\(\frac{1}{3}=\frac{1.15}{3.15}=\frac{15}{45}\)
\(\frac{2}{15}=\frac{2.3}{15.3}=\frac{6}{45}\)
Còn \(\frac{4}{45}\)ta giữ nguyên.
Bài 1:
a)
\(\dfrac{1}{2}=\dfrac{1\times6}{2\times6}=\dfrac{6}{12}\)
\(\dfrac{2}{3}=\dfrac{2\times4}{3\times4}=\dfrac{8}{12}\)
\(\dfrac{3}{4}=\dfrac{3\times3}{4\times3}=\dfrac{9}{12}\)
b)
\(\dfrac{1}{3}=\dfrac{1\times15}{3\times15}=\dfrac{15}{45}\)
\(\dfrac{2}{15}=\dfrac{2\times3}{15\times3}=\dfrac{6}{45}\)
\(\dfrac{4}{45}\) (giữ nguyên)
c)
\(\dfrac{1}{8}=\dfrac{1\times3}{8\times3}=\dfrac{3}{24}\)
\(\dfrac{2}{3}=\dfrac{2\times8}{3\times8}=\dfrac{16}{24}\)
\(\dfrac{5}{2}=\dfrac{5\times12}{2\times12}=\dfrac{60}{24}\)
d)
\(\dfrac{2}{7}=\dfrac{2\times4}{7\times4}=\dfrac{8}{28}\)
\(\dfrac{9}{4}=\dfrac{9\times7}{4\times7}=\dfrac{63}{28}\)
\(\dfrac{5}{28}\) (giữ nguyên)
Bài 2:
a)
\(4=\dfrac{4}{1}=\dfrac{4\times12}{1\times12}=\dfrac{48}{12}\)
\(\dfrac{9}{4}=\dfrac{9\times3}{4\times3}=\dfrac{27}{12}\)
b)
\(\dfrac{5}{8}=\dfrac{5\times30}{8\times30}=\dfrac{150}{240}\)
\(\dfrac{25}{30}=\dfrac{5}{6}=\dfrac{5\times40}{6\times40}=\dfrac{200}{240}\)
\(2=\dfrac{2}{1}=\dfrac{2\times240}{1\times240}=\dfrac{480}{240}\).
\(\frac{13}{15}=1-\frac{2}{15};\frac{45}{47}=1-\frac{2}{47}\)
\(\text{mà }\frac{2}{15}>\frac{2}{47}\Rightarrow\frac{13}{15}< \frac{45}{47}\)
\(\frac{35}{65}=1-\frac{30}{65};\frac{17}{47}=1-\frac{30}{47}\)
\(\text{mà }\frac{30}{65}< \frac{30}{47}\Rightarrow\frac{35}{15}>\frac{17}{47}\)
\(\frac{2}{3}+\frac{2}{15}+\frac{2}{35}+...+\frac{2}{101.103}\)
\(\Rightarrow\frac{2}{1}-\frac{2}{3}+\frac{2}{3}-\frac{2}{5}+...+\frac{2}{101}-\frac{2}{103}\)
\(\Rightarrow2-\frac{2}{103}=\frac{204}{103}\)
\(\frac{4}{1.5}+\frac{4}{5.9}+...+\frac{4}{101.105}\)
\(\Rightarrow4-\frac{4}{5}+\frac{4}{5}-\frac{4}{9}+...+\frac{4}{101}-\frac{4}{105}\)
\(\Rightarrow4-\frac{4}{105}=\frac{416}{105}\)