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`9/2xx7/3-4/3xx9/2`
`=9/2xx(7/3-4/3)`
`=9/2xx3/3`
`=9/2xx1`
`=9/2`
4/9 x 11 + 4/11 x 13 + 4/13 x 15 + ... + 4/97 x 99
= 2(1/9 - 1/11 + 1/11 - 1/13 + ... + 1/97 - 1/99)
= 2(1/9 - 1/99)
= 20/99
Chúc bạn học tốt!
a ) 42 x 99 + 42
= 42 x 99 + 42 x 1
= 42 x ( 99 + 1 )
= 42 x 100
= 4200
b ) 28 : 4 - 12 : 4
= ( 28 - 12 ) : 4
= 16 : 4
= 4
\(A=\dfrac{4}{3.7}+\dfrac{4}{7.11}+\dfrac{4}{11.15}+\dfrac{4}{15.19}+\dfrac{4}{19.23}+\dfrac{4}{23.27}\)(Dấu . là dấu nhân)
\(=\dfrac{1}{3}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{15}+\dfrac{1}{15}-\dfrac{1}{19}+\dfrac{1}{19}-\dfrac{1}{23}+\dfrac{1}{23}-\dfrac{1}{27}\)
\(=\dfrac{1}{3}-\dfrac{1}{27}\)
\(=\dfrac{9}{27}-\dfrac{1}{27}\)
\(=\dfrac{8}{27}\)
A = 4/3x7 + 4/7x11+ 4/11x15 + 4/15x19 + 4/19 x23 + 4/23 x 27
A = 1/3-1/7+1/7-1/11+1/11-1/15+1/15-1/19+1/19-1/23+1/23 -1/27
A = 1/3 - 1/27
A = 8/27
`3/4 xx4/5 +3/4xx8/5-3/4xx7/5`
`=3/4xx(4/5+8/5-7/5)`
`=3/4xx5/5`
`=3/4xx1`
`=3/4`
ღYêᑌ_ ᒪღ
`3/4 xx 4/5 + 3/4 xx 8/5 - 3/4 xx 7/5`
`=3/4 xx (4/5 + 8/5 -7/5)`
`= 3/4 xx 5/5`
`= 3/4 xx 1`
`= 3/4`
=7740000
\(=\left(4.25\right)+\left(215.6\right)+\left(12.5\right)\)
\(=100+1260+60\)
\(=1450\)