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\(\frac{11}{9}-\frac67\)
\(=\frac{77}{63}-\frac{54}{63}=\frac{77-54}{63}=\frac{23}{63}\)
\(\frac{7}{10}-\frac25=\frac{7}{10}-\frac{4}{10}=\frac{7-4}{10}=\frac{3}{10}\)
\(\frac72-2=\frac72-\frac42=\frac{7-4}{2}=\frac32\)
\(\frac65\times\frac38=\frac{6\times3}{5\times8}=\frac{18}{40}=\frac{9}{20}\)
\(\frac25:\frac32=\frac25\times\frac23=\frac{2\times2}{5\times3}=\frac{4}{15}\)
\(5:\frac57=5\times\frac75=7\)
\(\frac73:4=\frac{7}{3\times4}=\frac{7}{12}\)
911−76
\(= \frac{77}{63} - \frac{54}{63} = \frac{77 - 54}{63} = \frac{23}{63}\)
\(\frac{7}{10} - \frac{2}{5} = \frac{7}{10} - \frac{4}{10} = \frac{7 - 4}{10} = \frac{3}{10}\)
\(\frac{7}{2} - 2 = \frac{7}{2} - \frac{4}{2} = \frac{7 - 4}{2} = \frac{3}{2}\)
\(\frac{6}{5} \times \frac{3}{8} = \frac{6 \times 3}{5 \times 8} = \frac{18}{40} = \frac{9}{20}\)
\(\frac{2}{5} : \frac{3}{2} = \frac{2}{5} \times \frac{2}{3} = \frac{2 \times 2}{5 \times 3} = \frac{4}{15}\)
\(5 : \frac{5}{7} = 5 \times \frac{7}{5} = 7\)
\(\frac{7}{3} : 4 = \frac{7}{3 \times 4} = \frac{7}{12}\)
= 1 x 3 + 2 x 3 + 3 x 3 + 4 x 3 + ...+ 9 x 3
= 3 x ( 1 + 2 + 3 + 4 + ...+ 9)
= 3 x 45
= 135
a)\(2-3+5-7+9-11+13-15+17=\left(2+5+9+13+17\right)-\left(3+7+11+15\right)\)
\(=46-36=10\)
b)\(\frac{1}{1.2}+\frac{1}{2.3}+...............+\frac{1}{8.9}=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+.................+\frac{1}{8}-\frac{1}{9}\)
\(=\frac{1}{1}-\frac{1}{9}=\frac{9}{9}-\frac{1}{9}=\frac{8}{9}\)
Áp dụng \(\frac{1}{n.\left(n+1\right)}=\frac{1}{n}-\frac{1}{n+1}\)
Chúc bạn học tốt
Đề là tính bằng cách hợp lý đúng ko bạn
a, 2-3+5-7+9-11+13-15+17
= (5+13) - (3+15) + (2+9-11) + (17-7)
= 18 - 18 + 0 +10
= 10
b, \(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+\frac{1}{8\cdot9}\)
\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}\)
\(=1-\frac{1}{9}\)
\(=\frac{8}{9}\)
\(\dfrac{8}{9}:\dfrac{3}{7}=\dfrac{56}{27}\\ \dfrac{8}{9}+\dfrac{2}{5}=\dfrac{58}{45}\\ \dfrac{7}{8}-\dfrac{1}{3}=\dfrac{13}{24}\\ \dfrac{3}{10}\times\dfrac{1}{6}=\dfrac{1}{20}\\ 1\dfrac{2}{7}+6\dfrac{5}{6}=\dfrac{9}{7}+\dfrac{41}{6}=\dfrac{341}{42}\\ 5\dfrac{3}{4}-\dfrac{1}{5}=\dfrac{23}{4}-\dfrac{1}{5}=\dfrac{111}{20}\\ 6\dfrac{2}{9}:4\dfrac{7}{10}=\dfrac{56}{9}:\dfrac{47}{10}=\dfrac{560}{423}\\ \dfrac{5}{3}+\dfrac{3}{2}-\dfrac{7}{6}=2\)
a) \(\frac{59}{42}\)
b) \(\frac{17}{36}\)
c) \(\frac{5}{51}\)
d) \(\frac{4}{7}\)
a: \(\frac56+\frac47=\frac{35}{42}+\frac{24}{42}=\frac{35+24}{42}=\frac{59}{42}\)
b: \(\frac54-\frac79=\frac{45}{36}-\frac{28}{36}=\frac{45-28}{36}=\frac{17}{36}\)
c: \(\frac{15}{17}\times\frac19=\frac{15\times1}{17\times9}=\frac{15}{153}=\frac{5}{51}\)
d: \(\frac37:\frac68=\frac37:\frac34=\frac37\times\frac43=\frac47\)
bn ghi rõ đề bài ra nhé (1/3 + 5/8... 5/2 + 2/5) thì phần ... Là jv?
a)
1/3 + 5/8 = 8/24 + 15/24 = 23/24
5/2 + 2/5 = 25/10 + 4/10 = 29/10
3/8 + 2/3 = 9/24 + 16/24 = 25/24
2/3 + 4/9 = 6/9 + 4/9 = 10/9
b)
1/4 + 2/3 = 3/12 + 8/12 = 11/12
3/5 + 5/6 = 18/30 + 25/30 = 43/30
4/6 + 5/7 = 2/3 + 5/7 = 14/21 + 15/21 = 29/21
7/9 + 8/9 = 15/9 = 5/3
c)
2/3 + 7/6 = 4/6 + 7/6 = 11/6
8/3 + 3/7 = 56/21 + 9/21 = 65/21
9/4 + 11/6 = 27/12 + 22/12 = 49/12
8/5 + 1/3 = 24/15 + 5/15 = 29/15
a)
1/3 + 5/8 = 8/24 + 15/24 = 23/24
5/2 + 2/5 = 25/10 + 4/10 = 29/10
3/8 + 2/3 = 9/24 + 16/24 = 25/24
2/3 + 4/9 = 6/9 + 4/9 = 10/9
b)
1/4 + 2/3 = 3/12 + 8/12 = 11/12
3/5 + 5/6 = 18/30 + 25/30 = 43/30
4/6 + 5/7 = 2/3 + 5/7 = 14/21 + 15/21 = 29/21
7/9 + 8/9 = 15/9 = 5/3
c)
2/3 + 7/6 = 4/6 + 7/6 = 11/6
8/3 + 3/7 = 56/21 + 9/21 = 65/21
9/4 + 11/6 = 27/12 + 22/12 = 49/12
8/5 + 1/3 = 24/15 + 5/15 = 29/15
a) \(\frac13+\frac58=\frac{8}{24}+\frac{15}{24}=\frac{23}{24}\)
\(\frac52+\frac25=\frac{25}{10}+\frac{4}{10}=\frac{29}{10}\)
\(\frac38+\frac23=\frac{9}{24}+\frac{16}{24}=\frac{25}{24}\)
\(\frac23+\frac49=\frac69+\frac49=\frac{10}{9}\)
b) \(\frac14+\frac23=\frac{3}{12}+\frac{8}{12}=\frac{11}{12}\)
\(\frac35+\frac57=\frac23+\frac57=\frac{14}{21}+\frac{15}{21}=\frac{29}{21}\)
\(\frac79+\frac89=\frac{15}{9}=\frac53\)
c) \(\frac23+\frac76=\frac46+\frac76=\frac{11}{6}\)
\(\frac23+\frac37=\frac{56}{21}+\frac{9}{21}=\frac{65}{21}\)
\(\frac94+\frac{11}{6}=\frac{27}{12}+\frac{22}{12}=\frac{49}{12}\)
\(\frac85+\frac13=\frac{24}{15}+\frac{5}{15}=\frac{29}{15}\)
Phần a
- \(\frac{1}{3} + \frac{5}{8}\):
- \(\frac{5}{2} + \frac{2}{5}\):
- \(\frac{3}{8} + \frac{2}{3}\):
- \(\frac{2}{3} + \frac{4}{9}\):
Phần b\(\frac{1 \times 8}{3 \times 8} + \frac{5 \times 3}{8 \times 3} = \frac{8}{24} + \frac{15}{24} = \mathbf{\frac{23}{24}}\)
\(\frac{5 \times 5}{2 \times 5} + \frac{2 \times 2}{5 \times 2} = \frac{25}{10} + \frac{4}{10} = \mathbf{\frac{29}{10}}\)
\(\frac{3 \times 3}{8 \times 3} + \frac{2 \times 8}{3 \times 8} = \frac{9}{24} + \frac{16}{24} = \mathbf{\frac{25}{24}}\)
\(\frac{2 \times 3}{3 \times 3} + \frac{4}{9} = \frac{6}{9} + \frac{4}{9} = \mathbf{\frac{10}{9}}\)
- \(\frac{1}{4} + \frac{2}{3}\):
- \(\frac{3}{5} + \frac{5}{6}\):
- \(\frac{4}{6} + \frac{5}{7}\):
- \(\frac{7}{9} + \frac{8}{9}\):
Phần c\(\frac{1 \times 3}{4 \times 3} + \frac{2 \times 4}{3 \times 4} = \frac{3}{12} + \frac{8}{12} = \mathbf{\frac{11}{12}}\)
\(\frac{3 \times 6}{5 \times 6} + \frac{5 \times 5}{6 \times 5} = \frac{18}{30} + \frac{25}{30} = \mathbf{\frac{43}{30}}\)
\(\frac{2}{3} + \frac{5}{7} = \frac{2 \times 7}{3 \times 7} + \frac{5 \times 3}{7 \times 3} = \frac{14}{21} + \frac{15}{21} = \mathbf{\frac{29}{21}}\)
\(\frac{7 + 8}{9} = \frac{15}{9} = \mathbf{\frac{5}{3}}\)
\(\frac{2 \times 2}{3 \times 2} + \frac{7}{6} = \frac{4}{6} + \frac{7}{6} = \mathbf{\frac{11}{6}}\)
\(\frac{8 \times 7}{3 \times 7} + \frac{3 \times 3}{7 \times 3} = \frac{56}{21} + \frac{9}{21} = \mathbf{\frac{65}{21}}\)
\(\frac{9 \times 3}{4 \times 3} + \frac{11 \times 2}{6 \times 2} = \frac{27}{12} + \frac{22}{12} = \mathbf{\frac{49}{12}}\)
\(\frac{8 \times 3}{5 \times 3} + \frac{1 \times 5}{3 \times 5} = \frac{24}{15} + \frac{5}{15} = \mathbf{\frac{29}{15}}\)