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NT
0
26 tháng 10 2017
A=(\(\dfrac{1}{3}-\dfrac{1}{3}\))\(+\left(\dfrac{3}{5}+\left(\dfrac{-3}{5}\right)\right)+\left(\dfrac{-5}{7}+\dfrac{5}{7}\right)+\left(\dfrac{-7}{9}+\dfrac{7}{9}\right)\)\(+\left(\dfrac{-11}{13}-\dfrac{9}{11}\right)\)
A\(=0+0+0+0+\dfrac{-238}{143}\)
A\(=\dfrac{-238}{143}\)
\(B=\left(1+\dfrac{1}{2}\right)+\left(1+\dfrac{1}{4}\right)+\left(1+\dfrac{1}{8}\right)+\left(1+\dfrac{1}{32}\right)+\left(1+\dfrac{1}{64}\right)-7\)
\(B=\left(1+1+1+1+1\right)+\left(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}\right)-7\)
\(B=6+\dfrac{63}{64}-7\)
\(B=-1+\dfrac{63}{64}\)
\(B=\dfrac{-1}{64}\)
KV
26 tháng 12 2023
a) 2/3 + 3/4 . (-4/9)
= 2/3 - 1/3
= 1/3
b) -5/7 . 31/33 + (-5/7) : 33/2
= -5/7 . 31/33 - 5/7 . 2/33
= -5/7 . (31/33 + 2/33)
= -5/7 . 1
= -5/7
c) -3/5 . 13/11 - (-3/5) . 2/11
= -3/5 . (13/11 - 2/11)
= -3/5 . 1
= -3/5
QN
17 tháng 7 2019
a)4,1×3,5+4,1×7,5-4,1
= 4,1 x ( 3,5 + 7,5 ) - 4,1
= 4, 1x 11 - 4,1
= 45,1 - 4,1
= 41
b) 1/1998 × 2/7 + 1/1998 × 1
= 1/1998 x ( 2/7 + 1 )
= 1/1998 x 9/7
= 1/1554
3/7 - 5/1998 × 1/7
= 3/7 - 5/13986
= 5989/13986
k) [( 2/139 - 3/386)× 139/17 + 33/34] : [(7/2001 + 11/4002) × 201/25 + 9/2]
= [ 355/53654 x 139/17 + 33/34 ] : [ 25/4002 x 201/25 + 9/2 ]
= [ 355/6562 + 33/34 ] : [ 67/1334 + 9/2 ]
= 3362/3281 : 3035/667
= 0,2251949344
VM
17 tháng 7 2019
a) \(4,1.3,5+4,1.7,5-4,1\)
= \(4,1.\left(3,5+7,5\right)-4,1\)
= \(4,1.11-4,1\)
= \(45,1-4,1\)
= \(41\).
b) \(\frac{1}{1998}.\frac{2}{7}+\frac{1}{1998}.1\)
= \(\frac{1}{1998}.\left(\frac{2}{7}+1\right)\)
= \(\frac{1}{1998}.\frac{9}{7}\)
= \(\frac{1}{1554}\).
\(\frac{3}{7}-\frac{5}{1998}.\frac{1}{7}\)
= \(\frac{3}{7}-\frac{5}{13986}\)
= \(\frac{5989}{13986}\).
Chúc bạn học tốt!
TG
27 tháng 6 2020
a) \(-\frac{9}{13}.\frac{12}{29}-\frac{9}{13}.\frac{17}{29}+\frac{24}{13}\)
\(=-\frac{9}{13}\left(\frac{12}{29}+\frac{17}{29}\right)+\frac{24}{13}\)
\(=-\frac{9}{13}+\frac{24}{13}=\frac{15}{13}\)
b)\(\left(\frac{5}{3}-\frac{2}{11}\right):\frac{49}{33}+\left(-\frac{3}{7}\right)^2-\left|\frac{1}{7}-\frac{1}{14}\right|\)
\(=\left(\frac{5}{3}-\frac{2}{11}\right).\frac{33}{49}+\frac{9}{49}-\left|\frac{2}{14}-\frac{1}{14}\right|\)
\(=\frac{49}{33}.\frac{33}{49}+\frac{9}{49}-\frac{1}{14}\)
\(=1+\frac{9}{49}-\frac{1}{14}=\frac{49}{49}+\frac{9}{49}-\frac{1}{14}\)
\(=\frac{58}{49}-\frac{1}{14}=\frac{109}{98}\)
OT
1
10 tháng 8 2020
\(S=1+\frac{1}{2}+1+\frac{1}{4}+1+\frac{1}{8}+1+\frac{1}{16}+1+\frac{1}{32}+1+\frac{1}{64}-7\)
\(S=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}-1\)
Ta đặt: \(P=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)
=> \(2P=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\)
=> \(2P-P=\left(1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}\right)-\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\right)\)
=> \(P=1-\frac{1}{64}\)
Mà \(S=P-1\)
=> \(S=1-\frac{1}{64}-1=-\frac{1}{64}\)
Vậy \(S=-\frac{1}{64}\)