3 * 7 = ? giúp mình với
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Trả lời:
\(\frac{32}{28}\times\frac{7}{6}=\)\(\frac{8}{7}\times\frac{7}{6}=\)\(\frac{56}{42}=\frac{4}{3}\)
^_^
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Trả lời:
32/28x7/6=8/7x7/6=56/42=4/3
hok tốt !
k cho mik nhé
^_^
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{3}{7}+\dfrac{5}{7}+1+3+4+\dfrac{2}{7}+\dfrac{4}{7}+2=\left(\dfrac{3}{7}+\dfrac{5}{7}+\dfrac{2}{7}+\dfrac{4}{7}\right)+\left(1+3+4+2\right)=2+10=12\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(=\dfrac{3}{7}\left(-\dfrac{15}{13}-\dfrac{11}{13}-1\right)=\dfrac{3}{7}\left(-2-1\right)=-\dfrac{9}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Quy đồng phân số ta được
45/105<.../105<60/105
Sau khi tìm tử số ta được phân số 49/105 rút gọn được 7/15 ( thỏa mãn)
Vậy số cần tìm là 7
học tốttt
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(S=\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{40.43}+\frac{3}{43.46}\)
\(S=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{40}-\frac{1}{43}+\frac{1}{43}-\frac{1}{46}\)
\(S=1-\frac{1}{46}< 1\)
Chứng tỏ S < 1
Ủng hộ mk nha ^_^
S = \(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+......+\frac{3}{43.46}\)
\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+.....+\frac{1}{43}-\frac{1}{46}\)
\(=1-\frac{1}{46}=\frac{45}{46}< 1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
3/25 x ( 15/7 - 2/7 ) + 3/7 x 1/25
= 3/25 x 13/7 + 3/7 x 1/25
= (3 x 13/7 + 3/7 ) x 1/25
= 42/7 x 1/25
= 6 x 1/25
= 6/25
\(\dfrac{3}{25}\times\dfrac{15}{7}+\dfrac{3}{7}\times\dfrac{1}{25}-\dfrac{2}{7}\times\dfrac{3}{25}\)
\(=\dfrac{3}{25}\times\left(\dfrac{15}{7}-\dfrac{2}{7}\right)+\dfrac{3}{7}\times\dfrac{1}{25}\)
\(=\dfrac{3}{25}\times\dfrac{13}{7}+\dfrac{3}{7}\times\dfrac{1}{25}\)
\(=\dfrac{3\times13}{25\times7}+\dfrac{3\times1}{7\times25}\)
\(=\dfrac{39}{175}+\dfrac{3}{175}\)
\(=\dfrac{39+3}{175}\)
\(=\dfrac{42}{175}\)
\(=\dfrac{6}{25}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
b) -3.7^4 + 7^3 / 7^5 . 6 - 7^3 .2
= -21 . 7^3 + 7^3 . 1 / 7^3 . 294 - 7^3 . 2
= 7^3 . (-21+1) / 7^3 . (294 - 2)
= 20/292 = 5/73
Tui Hông Hỉu, Dải Đáp Cho Tui Dới.............................
![](https://rs.olm.vn/images/avt/0.png?1311)
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3*7=21 bạn nha
CHÚC BẠN HỌC GIỎI
21 nha