TÍNH\(\frac{3X5X7}{21X10}\)
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TÍNH\(\frac{3X5X7}{21X10}\)
\(\frac{3X5X7}{21X10}=\frac{105}{210}\)
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\(\frac{3x5x7}{21x10}=\frac{5}{10}=\frac{1}{2}\)
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3x5x7/21x10 tìm phân số tối giản
\(\frac{3\cdot5\cdot7}{21\cdot10}=\frac{21\cdot5}{21\cdot10}=\frac{1}{2}\)
tk cho mk nhé.
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tính nhanh \(\frac{\left(2^3x5x7\right)x\left(5^2x7^3\right)}{\left(2x5x7^2\right)^2}\)
\(A=\frac{3x5x7+6x10x14+9x15x21}{5x7x9+10x14x18+15x21x27}\)
\(\frac{3.5.7+6.10.14+9.15.21}{5.7.9+10.14.18+15.21.27}\)
= \(\frac{3.5.7+3.2.5.2.7.2+3.3.5.3.7.21}{5.7.9+5.2.7.2.9.2+5.3.7.3.9.3}\)
= \(\frac{3.5.7+3.5.7.2.2.2+3.5.7.3.3.3}{5.7.9+5.7.9.2.2.2+5.7.9.3.3.3}\)
= \(\frac{3.5.7+3.5.7.8+3.5.7.27}{5.7.9+5.7.9.8+5.7.9.27}\)
= \(\frac{3.5.7.\left(1+8+27\right)}{5.7.9.\left(1+8+27\right)}\)
= \(\frac{3.5.7.36}{5.7.9.36}\)
= \(\frac{1}{3}\)
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Tính tổng : S =1x3x5+3x5x7+5x7x9+...+21x23x25
tính nhanh :
4/1x3x5 + 4/3x5x7 + 4/5x7x9 + 4/7x9x11 + 4/9x11x13 .
tính nhanh 4/1x3x5+4/3x5x7+4/5x7x9+4/7x9x11+4/9x11x13
Bài 7: tính nhanh
3/1x3x5+3/3x5x7+3/5x7x9+...+3/37x39x41
cíu emmmmmmmmmmmm
\(\dfrac{3}{1\cdot3\cdot5}+\dfrac{3}{3\cdot5\cdot7}+\dfrac{3}{5\cdot7\cdot9}+\cdot\cdot\cdot+\dfrac{3}{37\cdot39\cdot41}\)
\(=\dfrac{3}{4}\left(\dfrac{4}{1\cdot3\cdot5}+\dfrac{4}{3\cdot5\cdot7}+\dfrac{4}{5\cdot7\cdot9}+\cdot\cdot\cdot+\dfrac{4}{37\cdot39\cdot41}\right)\)
\(=\dfrac{3}{4}\left(\dfrac{1}{1\cdot3}-\dfrac{1}{3\cdot5}+\dfrac{1}{3\cdot5}-\dfrac{1}{5\cdot7}+\dfrac{1}{5\cdot7}-\dfrac{1}{7\cdot9}+\cdot\cdot\cdot+\dfrac{1}{37\cdot39}-\dfrac{1}{39\cdot41}\right)\)
\(=\dfrac{3}{4}\left(\dfrac{1}{3}-\dfrac{1}{39\cdot41}\right)\)
\(=\dfrac{3}{4}\cdot\dfrac{532}{1599}=\dfrac{133}{533}\)
#Ayumu
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\(\frac{4}{1x3x5}\)+\(\frac{4}{3x5x7}\)+\(\frac{4}{5x7x9}\)+......+\(\frac{4}{93x95x97}\)+\(\frac{4}{95x97x99}\)