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1/2 x(1+2) + 1/3 x(1+2+3) + 1/4 x (1+2+3+4) +......+1/16x(1+2+....+16)
=1/2x (2.3/2) + 1/3x( 3.4/2)+....+ 1/16x (16.17/2)
=3/2+4/2+...+17/2
=1/2 (3+4+...+17)
=1/2x 150
=75
( 1 - 1/2 ) + ( 1 - 1/3 ) + ( 1 - 1/4 ) + ( 1 - 1/5 )
= ( 2/2 - 1/2 ) + ( 3/3 - 1/3 ) + ( 4/4 - 1/4 ) + ( 5/5 - 1/5 )
= 1/2 + 2/3 + 3/4 + 4/5
= ( 1/2 + 3/4 ) + ( 2/3 + 4/5 )
= ( 2/4 + 3/4 ) + ( 10/15 + 12/15 )
= 5/4 + 22/15
= 75/60 + 88/60
= 163/60
\(5\dfrac{9}{10}:\dfrac{3}{2}-\left(2\dfrac{1}{3}\times4\dfrac{1}{2}-2\times2\dfrac{1}{3}\right):\dfrac{7}{4}\)
\(=\dfrac{59}{10}:\dfrac{3}{2}-\left(\dfrac{7}{3}\times\dfrac{9}{2}-2\times\dfrac{7}{3}\right):\dfrac{7}{4}\)
\(=\dfrac{59}{10}\cdot\dfrac{2}{3}-\left[\dfrac{7}{3}\times\left(\dfrac{9}{2}-2\right)\right]:\dfrac{7}{4}\)
\(=\dfrac{59}{15}-\left(\dfrac{7}{3}\times\dfrac{5}{2}\right):\dfrac{7}{4}\)
\(=\dfrac{59}{15}-\dfrac{35}{6}\cdot\dfrac{4}{7}\)
\(=\dfrac{59}{15}-\dfrac{10}{3}\)
\(=\dfrac{59}{15}-\dfrac{50}{15}\)
\(=\dfrac{9}{15}\)
\(=\dfrac{3}{5}\)
\(Toru\)
9/10 ban nhe
9/10
k mk nha các ban