tính nhanh (1 - 1/2) * (1 - 1/3) * (1 - 1/4) * (1 - 1/5)* (1 - 1/6)
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\(\frac{1}{1}\times\frac{1}{2}+\frac{1}{2}\times\frac{1}{3}+\frac{1}{3}\times\frac{1}{4}+\frac{1}{4}\times\frac{1}{5}+\frac{1}{5}\times\frac{1}{6}=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}\)
\(=\frac{30}{60}+\frac{10}{60}+\frac{5}{60}+\frac{3}{60}+\frac{2}{60}\)
\(=\frac{50}{60}=\frac{5}{6}\)
Đáp án là 5/6 tick nha bạn
(1/2+1/3+1/4+1/5+1/6+1/7)−(1/3+1/4+1/5+1/6+1/7+1/8)
= (1/2+1/8 )+(1/4+1/6 )+(1/6+1/4)−(1/3+1/7 )-(1/5 + 1/5 )
= 1/10 +1/10 +1/10 +1/10 -1/10
= 4/10 = 2/5
k mk na <3
1/2 + ( 1/3 - 1/3 ) + ( 1/4 - 1/4 ) + ( 1/5 -1/5 ) + ( 1/6 - 1/6 ) + ( 1/7 - 1/7 ) + 1/8
= 1/2 + 0 + 1/8
= 5/8
= \(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
= \(1-\frac{1}{6}=\frac{5}{6}\)
\(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{1}{6}-\frac{1}{5}-\frac{1}{4}-\frac{1}{3}-\frac{1}{2}\)
\(=\left(\frac{1}{2}-\frac{1}{2}\right)+\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{1}{4}-\frac{1}{4}\right)+\left(\frac{1}{5}-\frac{1}{5}\right)+\frac{1}{6}\)
\(=0+0+0+0+\frac{1}{6}\)
\(=\frac{1}{6}\)
_Chúc bạn học tốt_
\(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{1}{6}-\frac{1}{5}-\frac{1}{4}-\frac{1}{3}-\frac{1}{2}\)
\(=\left(\frac{1}{2}-\frac{1}{2}\right)+\left(\frac{1}{3}-\frac{1}{3}\right)+\left(\frac{1}{4}-\frac{1}{4}\right)+\left(\frac{1}{5}-\frac{1}{5}\right)+\frac{1}{6}\)
\(=0+0+0+0+\frac{1}{6}\)
\(=\frac{1}{6}\)
\(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}+\dfrac{1}{7\times8}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}\)
\(=1-\dfrac{1}{8}=\dfrac{7}{8}\)
\(\frac{1}{2}-\frac{1}{-3}+\frac{1}{-3}.\frac{1}{4}+\frac{1}{4}.\frac{1}{-5}+\frac{1}{-5}.\frac{1}{6}\)1/6
\(=\frac{1}{2}+\frac{1}{3}-\frac{1}{3}.\frac{1}{4}+\left(\frac{1}{4}+\frac{1}{6}\right).\frac{-1}{5}\)
\(=\frac{5}{6}-\frac{1}{12}+\frac{5}{6}.\frac{-1}{5}\)
\(=\frac{7}{12}\)
1/2 × 1/2 + 1/2 × 1/3 + 1/3 × 1/4 + 1/4 × 1/5 + 1/5 × 1/6
= 1/4 + 1/2×3 + 1/3×4 + 1/4×5 + 1/5×6
= 1/4 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6
= 1/4 + 1/2 - 1/6
= 3/12 + 6/12 - 2/12
= 9/12 - 2/12
= 7/12
(1-\(\frac{1}{2}\)) x ( 1- \(\frac{1}{3}\))x ( 1-\(\frac{1}{4}\))x(1-\(\frac{1}{5}\)) x (1 -\(\frac{1}{6}\))
= (\(\frac{2}{2}\)-\(\frac{1}{2}\)) x (\(\frac{3}{3}\)-\(\frac{1}{3}\)) x (\(\frac{4}{4}\)- \(\frac{1}{4}\)) x (\(\frac{5}{5}\)-\(\frac{1}{5}\)) x ( \(\frac{6}{6}\)-\(\frac{1}{6}\))
= \(\frac{1}{2}\)x \(\frac{2}{3}\)x\(\frac{3}{4}\)x\(\frac{4}{5}\)x\(\frac{5}{6}\)
= \(\frac{1X2X3X4X5}{2X3X4X5X6}\)
=\(\frac{1}{6}\)( bạn dùng cách rút gọn nha )
=1/6 nhé bạn