A=2/1×3+2/3×5+2/5×7+2/7×9+...2/2017×2019
Mn giúp e vs e cần gấp
K
Khách
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Những câu hỏi liên quan
LH
1
PT
Phạm Trần Hoàng Anh
CTVHS
26 tháng 6 2020
A = 1-1/3 + 1/3 - 1/5 +...+ 1/2017 - 1/2019
A= 1-1/2019
A= 2018/2019
10 tháng 11 2018
D = 1 . 2 + 2 . 3 + 3 . 4 + 4 . 5 + .... + 99 . 100 + 100 . 101
3D=1 . 2 . 3 + 2 . 3 . ( 4 - 1 ) + 3 . 4 . ( 5 - 2 )+ 4 . 5 + ( 6 - 3) + .... + 99. 100 . ( 101 - 98 ) + 100 . 101 . ( 102 - 99 )
3D=1 . 2 . 3+2 . 3 . 4-1 . 2 . 3 + 3 . 4 . 5 - 2 . 3 . 4 + 4 . 5 . 6 - 3 . 4 . 5 + ..... + 99 . 100 . 101- 98 . 99 . 100 +100 . 101 . 102-99.100.101
3D = 100 . 101 . 102
D = \(\frac{100.101.102}{3}=343400\)
E = \(2+2^3+2^5+2^7+...+2^{2017}+2^{2019}\)
4E = \(2^3+2^5+2^7+2^9...+2^{2019}+2^{2021}\)
=> 4E - E = \(2^3+2^5+2^7+2^9...+2^{2019}+2^{2021}\)- ( \(2+2^3+2^5+2^7+...+2^{2017}+2^{2019}\))
=> 3E = \(2^{2021}-2\)
=> E = \(\frac{2^{2021}-2}{3}\)
NA
Nguyễn An Ninh
VIP
25 tháng 4 2023
a\()\) 16/9 +3/5
=107/45
b\()\) 4/13--2/17
=51/221--26/221
=77/221
c\()\) -3/2+4/5
=-15/10+8/10
=-7/10
d\()\) 3/-4-1/4
=-1
e\()\) -1/5.5/7
=-1/7
f\()\) 7/8.64/49
=8/7
g\()\) 3/4.15/24
=15/32
C
11 tháng 2 2023
`#lv`
`-2/5+(-7/10)-9/6`
`=-2/5-7/10-9/6`
`=-4/10-7/10-9/6`
`=-11/10-3/2`
`=-11/10-15/10`
`=-26/10`
`=-13/5`
__
`1/2+(-2/5)-(-2/3)`
`=1/2-2/5+2/3`
`=5/10-4/10+2/3`
`=1/10+2/3`
`=3/30+20/30`
`=23/30`
__
`5/3-3/4+7/6`
`=20/12-9/12+14/12`
`=11/12+14/12`
`=25/12`
__
`-1/5+5/3-3/2`
`=-3/15+25/15-3/2`
`=22/15-3/2`
`=44/30-45/30`
`=-1/30`
__
`1/4-7/8+(-9/10)`
`=2/8-7/8-9/10`
`=-5/8-9/10`
`=-25/40-36/40`
`=-61/40`
__
`5/4+1/2+(-7/12)`
`=15/12+6/12-7/12`
`=21/12-7/12`
`=14/12`
`=7/6`
__
`-5/8-1/3+(-7/6)`
`=-5/8-1/3-7/6`
`=-15/24-8/24-28/24`
`=-52/24`
`=-13/6`
__
`-3/4-7/10+(-5/6)`
`=-3/4-7/10-5/6`
`=-45/60-42/60-50/60`
`=-137/60`
KH
11 tháng 2 2023
Bài làm
a, (-2/5) + (-7/10) - 9/6 =(-12/30) + (-21/30) - 45/30=(-33/30) - 45/30 = (-78/30)
b,1/2 + (-2/5) - (-2/3) = 15/30 + (-12/30) - (-20/30) = 3/30 - (-20/30) = 23/30
c,5/3 - 3/4 + 7/6 = 40/24 - 18/24 + 28/24 = 22/24 + 28/24 = 50/24 = 25/12
d, (-1/5) + 5/3 - 3/2 = (-6/30) + 50/30 - 45/30 = 44/30 - 45/30 = (-1/30)
e, 1/4 - 7/8 + (-9/10) = 10/40 - 35/40 - 36/40 = (-25/40) - 36/40 = (-61/40)
f, 5/4 +1/2 + (-7/12) = 15/12 + 6/12 - 7/12 = 21/12 - 7/12 = 14/12 = 7/6
g,(-5/8) -1/3 + (-7/6) = (-15/24) - 8/24 - 28/24 = (-23/24) - 28/24 = (-51/24)
k,(-3/4) - 7/10 + (-5/6) = (-45/60) - 42/60 - 50/60 = (-87/60) - 50/60 = (-137/60)
chúc bn học tốt nha
sai thì mn góp ý giúp mk
TT
0
LT
a)-4/11+5/6+7/11-5/6
b)-5/6.7/13+19/13.6/-5+2/5
c)3/7.(-0,5+3/2)-2/7:25%
mọi người giúp e vs ạ
e cần gấp
3
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
19 tháng 2
a; - \(\dfrac{4}{11}\) + \(\dfrac{5}{6}\) + \(\dfrac{7}{11}\) - \(\dfrac{5}{6}\)
= (-\(\dfrac{4}{11}\) + \(\dfrac{7}{11}\)) + (\(\dfrac{5}{6}\) - \(\dfrac{5}{6}\))
= - \(\dfrac{3}{11}\) + 0
= - \(\dfrac{3}{11}\)
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
19 tháng 2
b; -\(\dfrac{5}{6}\).\(\dfrac{7}{13}\) + \(\dfrac{19}{13}\).\(\dfrac{6}{-5}\) + \(\dfrac{2}{5}\)
= - \(\dfrac{35}{78}\) - \(\dfrac{114}{65}\) + \(\dfrac{2}{5}\)
= - \(\dfrac{859}{390}\) + \(\dfrac{2}{5}\)
= - \(\dfrac{703}{390}\)
10 tháng 11 2017
\(\text{a) }\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\\ =\dfrac{3\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)}{3}\\ =\dfrac{\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)}{3}\\ \\ =\dfrac{\left(2^4-1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)}{3}\\ =\dfrac{\left(2^8-1\right)\left(2^8+1\right)\left(2^{16}+1\right)}{3}\\ =\dfrac{\left(2^{16}-1\right)\left(2^{16}+1\right)}{3}\\ =\dfrac{2^{32}-1}{3}\\ \)
\(\text{b) }24\left(5^2+1\right)\left(5^4+1\right)\left(5^8+1\right)\left(5^{16}+1\right)\\ =\left(5^2-1\right)\left(5^2+1\right)\left(5^4+1\right)\left(5^8+1\right)\left(5^{16}+1\right)\\ =\left(5^4-1\right)\left(5^4+1\right)\left(5^8+1\right)\left(5^{16}+1\right) \\ =\left(5^8-1\right)\left(5^8+1\right)\left(5^{16}+1\right)\\ =\left(5^{16}-1\right)\left(5^{16}+1\right)\\ =5^{32}-1\\ \)
\(\text{c) }48\left(7^2+1\right)\left(7^4+1\right)\left(7^8+1\right)\left(7^{16}+1\right)\\ =\left(7^2-1\right)\left(7^2+1\right)\left(7^4+1\right)\left(7^8+1\right)\left(7^{16}+1\right)\\ =\left(7^4-1\right)\left(7^4+1\right)\left(7^8+1\right)\left(7^{16}+1\right)\\ =\left(7^8-1\right)\left(7^8+1\right)\left(7^{16}+1\right)\\ =\left(7^{16}-1\right)\left(7^{16}+1\right)\\ =7^{32}-1\)
Lời giải:
$A=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+..+\frac{2}{2017.2019}$
$=\frac{3-1}{1.3}+\frac{5-3}{3.5}+\frac{7-5}{5.7}+...+\frac{2019-2017}{2017.2019}$
$=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{2017}-\frac{1}{2019}$
$=1-\frac{1}{2019}=\frac{2018}{2019}$