12×7×275×6×7×9​=(6×2)×7×(9×3)5×6×7×9​

Rút gọn \(6 , 7 , 9\):

\(= \frac{5}{2 \times 3} = \frac{5}{6} .\)

✅ Kết quả: \(\frac{5}{6}\).

a)

\(\frac{3 \times 4 \times 7}{12 \times 8 \times 9}\)

• Tử số = \(3 \times 4 \times 7 = 84\).
• Mẫu số = \(12 \times 8 \times 9 = 864\).

\(\frac{84}{864} = \frac{84 \div 12}{864 \div 12} = \frac{7}{72} .\)

✅ Kết quả: \(\frac{7}{72}\).

b)

\(\frac{4 \times 5 \times 6}{12 \times 10 \times 8}\)

• Tử số = \(4 \times 5 \times 6 = 120\).
• Mẫu số = \(12 \times 10 \times 8 = 960\).

\(\frac{120}{960} = \frac{1}{8} .\)

✅ Kết quả: \(\frac{1}{8}\).

c)

\(\frac{5 \times 6 \times 7}{12 \times 14 \times 15}\)

• Tử số = \(5 \times 6 \times 7 = 210\).
• Mẫu số = \(12 \times 14 \times 15 = 2520\).

\(\frac{210}{2520} = \frac{1}{12} .\)

✅ Kết quả: \(\frac{1}{12}\).

👉 Kết quả cuối cùng:

• a) \(\frac{7}{72}\)
• b) \(\frac{1}{8}\)
• c) \(\frac{1}{12}\)

a) \(\dfrac{30\times25\times7\times8}{75\times8\times12\times14}=\dfrac{3\times2\times5\times25\times7\times8}{25\times3\times8\times3\times4\times2\times7}=\dfrac{5}{3\times4}=\dfrac{5}{12}\)

b) \(\dfrac{8\times3\times4}{16\times3}=\dfrac{8\times3\times2\times2}{8\times2\times3}=2\)

c) \(\dfrac{4\times5\times6}{3\times10\times8}=\dfrac{4\times5\times3\times2}{3\times5\times2\times4\times2}=\dfrac{1}{2}\)

giúp mik với ạ, mình sẽ tick ạ! Thanks.

giúp mình với! Thanks

M = (345 x (6789 + 3456 - 245)/690) x 99/100 x 98/99 x...x 2/3 x 1/2
M = ((345 x 10000)/690) x 99/2 (rút gọn)
M = (10000/2) x 99/2
M = 5000 x 99/2
M = 247500
Ok nha

\(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+....+\frac{1}{98\times99}+\frac{1}{99\times100}\)

\(=\frac{2-1}{1\times2}+\frac{3-2}{2\times3}+\frac{4-3}{3\times4}+....+\frac{99-98}{98\times99}+\frac{100-99}{99\times100}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{98}-\frac{1}{99}+\frac{1}{99}-\frac{1}{100}\)

\(=1-\frac{1}{100}\)

\(=\frac{99}{100}\)

\(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{98\cdot99}+\frac{1}{99\cdot100}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\)

\(=1-\frac{1}{100}\)

\(=\frac{99}{100}\)

rút gọn là được mà ! 

\(\frac{1}{2}\)

\(a,\frac{3\times4\times7}{12\times8\times9}\)

\(=\frac{3\times4\times7}{3\times4\times8\times9}\)

\(=\frac{7}{72}\)

\(b,\frac{4\times5\times6}{12\times10\times8}\)

\(=\frac{4\times5\times3\times2}{4\times3\times5\times2\times8}\)

\(=\frac{1}{8}\)

\(c,\frac{5\times6\times7\times9}{12\times7\times27}\)

\(=\frac{5\times6\times7\times9}{6\times2\times7\times9\times3}\)

\(=\frac{5}{6}\)

\(d,\frac{5\times6\times7}{12\times14\times15}\)

\(=\frac{5\times6\times7}{6\times2\times7\times2\times5\times3}\)

\(=\frac{1}{12}\)

a) \(\frac{3\times4\times7}{12\times8\times9}=\frac{3\times4\times7}{3\times4\times8\times9}=\frac{7}{8\times9}=\frac{7}{72}\)

b) \(\frac{4\times5\times6}{12\times10\times8}=\frac{4\times5\times6}{6\times2\times2\times5\times4\times2}=\frac{1}{2\times2\times2}=\frac{1}{8}\)

c) \(\frac{5\times6\times7\times9}{12\times7\times27}=\frac{5\times6\times9}{12\times27}=\frac{5\times6\times9}{2\times6\times3\times9}=\frac{5}{2\times3}=\frac{5}{6}\)

d) \(\frac{5\times6\times7}{12\times14\times15}=\frac{5\times6\times7}{2\times6\times2\times7\times3\times5}=\frac{1}{2\times2\times3}=\frac{1}{12}\)

a) $\frac{{14}}{{18}}:\frac{8}{9} = \frac{7}{9}:\frac{8}{9} = \frac{7}{9} \times \frac{9}{8} = \frac{{63}}{{72}} = \frac{7}{8}$

b) $\frac{9}{6}:\frac{3}{{10}} = \frac{3}{2}:\frac{3}{{10}} = \frac{3}{2} \times \frac{{10}}{3} = \frac{{30}}{6} = 5$

c) $\frac{4}{5}:\frac{{10}}{{15}} = \frac{4}{5}:\frac{2}{3} = \frac{4}{5} \times \frac{3}{2} = \frac{{12}}{{10}} = \frac{6}{5}$

d)  $\frac{1}{6}:\frac{{21}}{9} = \frac{1}{6}:\frac{7}{3} = \frac{1}{6} \times \frac{3}{7} = \frac{3}{{42}} = \frac{1}{{14}}$

nhân biểu thức vs 2. đcj bao nhiêu chia cho 2