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3/4+1/2+5/8=15/8
5/9+9/8-15/28=577/504
11/30-9/25x15/27=1/6
3/4:5/8:3/10=4
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\(\left(\frac{9}{2}-\frac{5}{2}\right)-\frac{3}{4}=\frac{4}{2}-\frac{3}{4}=\frac{8}{4}-\frac{3}{4}=\frac{5}{4}\)\(\frac{5}{4}\)
\(\frac{9}{2}-\left(\frac{5}{2}+\frac{3}{4}\right)=\frac{9}{2}-\left(\frac{10}{4}+\frac{3}{4}\right)=\frac{9}{2}-\frac{13}{4}=\frac{18}{4}-\frac{13}{4}=\frac{5}{4}\)
Vậy : \(\left(\frac{9}{2}-\frac{5}{2}\right)-\frac{3}{4}=\frac{9}{2}-\left(\frac{5}{2}+\frac{3}{4}\right)\)
tk mk nha
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Ta thấy mỗi số đều có cặp
Ta có :
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
Ta sẽ tính tổng từ 1->9
Số các số hạng là :
( 9 - 1 ) : 1 + 1 = 9 ( số )
Tổng các số là :
9 x ( 9 + 1 ) : 2 = 45
Vậy bây giờ ta nhân hai vì chúng có cặp :
=> = 2 X 45
= 90
\(A=1+2+3+4+5+6+7+8+9+1+2+3+4+5+6+7+8+9\)
\(A=2\times\left(1+9+2+8+3+7+4+6+5\right)\)
\(A=2\times\left(10+10+10+10+5\right)\)
\(A=2\times45=90\)
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Bài làm
a) \(\left(\frac{1}{2}+\frac{4}{7}\right)-\left(\frac{3}{7}-\frac{3}{10}\right)\)
\(=\frac{1}{2}+\frac{4}{7}-\frac{3}{7}+\frac{3}{10}\)
\(=\frac{35}{70}+\frac{40}{70}-\frac{30}{70}+\frac{21}{70}\)
\(=\frac{66}{70}\)
\(=\frac{33}{35}\)
b) \(\left(\frac{3}{5}x\frac{4}{5}x\frac{5}{9}\right):\left(\frac{7}{9}-\frac{3}{5}\right)\)
\(=\left(\frac{1}{5}x\frac{4}{3}\right):\left(\frac{35}{45}-\frac{27}{45}\right)\)
\(=\frac{4}{15}:\frac{8}{45}\)
\(=\frac{4}{15}.\frac{45}{8}\)
\(=\frac{1}{1}.\frac{3}{2}\)
\(=\frac{3}{2}\)
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\(5-\frac{13}{17}=\frac{5}{1}-\frac{13}{17}=\frac{85}{17}-\frac{13}{17}=\frac{72}{17}\)
\(\frac{2}{5}-\frac{1}{7}=\frac{14}{35}-\frac{5}{35}=\frac{9}{35}\)
\(\frac{4}{9}-\frac{2}{9}=\frac{4-2}{9}=\frac{2}{9}\)
\(\frac{5}{4}-\frac{1}{3}=\frac{15}{12}-\frac{4}{12}=\frac{11}{12}\)
\(\frac{5}{2}-\frac{1}{4}-\frac{2}{3}=\frac{30}{12}-\frac{3}{12}-\frac{8}{12}=\frac{19}{12}\)
\(\frac{4}{3}-\frac{2}{5}+\frac{1}{2}=\frac{40}{30}-\frac{12}{30}+\frac{15}{30}=\frac{40-12+15}{30}=\frac{53}{30}\)
tk cho mk,mk đang bị trừ điểm
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a, 9/1 * 3/8 + 3/8 * 9/7
b, 4/5 * 7/10 - 1/9 * 4/5
C1:nhân chia trước cộng trừ sau
C2:a,3,8x(9,1+9,7)=3,8x18,8=?
b,b, 4/5 * 7/10 - 1/9 * 4/5=4/5x(7/10-1/9)=?
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2/9+3/9+4/9+5/9+6/9+7/9
=2+3+4+5+6+7/9
=27/9
=3
1/6+4/9+5/6+11/16+5/9+5/16
=1/6+5/6+4/9+5/9+11/16+5/16
=1+1+1=3
hok tốt ~
Kết quả: 5 12