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DV
5 tháng 3 2017
15.1/5(1/90.94+1/84.98+...+1/146.150)
=3(1/90-1/94+1/94-1/98+...+1/146-1/150)
=3(1/90-1/150)
3.1/225
=1/75
LV
3
ML
30 tháng 6 2017
\(\frac{15}{90.94}+\frac{15}{94.98}+\frac{15}{98.102}+...+\frac{15}{146.150}\)
\(=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+\frac{1}{98}-\frac{1}{102}+...+\frac{1}{146}-\frac{1}{150}\right)\)
\(=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{150}\right)\)
\(=\frac{15}{4}.\frac{1}{225}\)
\(=\frac{1}{60}\)
DP
30 tháng 6 2017
\(\frac{15}{90\cdot94}+\frac{15}{94\cdot98}+\frac{15}{98\cdot102}+...+\frac{15}{146\cdot150}\)
\(=\frac{15}{4}\cdot\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+\frac{1}{98}-\frac{1}{102}+...+\frac{1}{146}-\frac{1}{150}\right)\)
\(=\frac{15}{4}\cdot\left(\frac{1}{90}-\frac{1}{150}\right)\)
\(=\frac{15}{4}\cdot\frac{1}{225}=\frac{1}{60}\)
DA
6
25 tháng 6 2016
a ) 15 / 90 x 94 + 15 / 94 x 98 + 15 / 98 x102+...+ 15 / 146 x 150
= 15/4 x ( 4/90 x 94 + 4/94 x 98 + ... + 4/ 146 x 150 )
= 15/4 x ( 1/90 - 1/94 + 1/94 - 1/98 + ... + 1/146 - 1/150 )
= 15/4 x ( 1/90 - 1/150 )
= 15/4 x 2/450
= 1/60
b ) 10 / 56 + 10/ 140 + 10 / 260+...+ 10 /1400
= 5/28 + 5/70 + 5/130 + ... + 5/700
= 5/4 x 7 + 5/7 x 10 + 5/10 x 13 + ... + 5 /25 x 28
= 5/3 x ( 3/4 x 7 + 3/7 x 10 + ... + 3/25 x 28 )
= 5/3 x ( 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/25 - 1/28 )
= 5/3 x ( 1/4 - 1/28 )
= 5/3 x 6/28
= 5/14
1 tháng 7 2016
ngài kiệt lí đây gian lận tuyệt vời.
vĩ đại như nước trong nguồn chảy ra.
7 tháng 2 2016
a ) 15 / 90 x 94 + 15 / 94 x 98 + 15 / 98 x102+...+ 15 / 146 x 150
= 15/4 x ( 4/90 x 94 + 4/94 x 98 + ... + 4/ 146 x 150 )
= 15/4 x ( 1/90 - 1/94 + 1/94 - 1/98 + ... + 1/146 - 1/150 )
= 15/4 x ( 1/90 - 1/150 )
= 15/4 x 2/450
= 1/60
b ) 10 / 56 + 10/ 140 + 10 / 260+...+ 10 /1400
= 5/28 + 5/70 + 5/130 + ... + 5/700
= 5/4 x 7 + 5/7 x 10 + 5/10 x 13 + ... + 5 /25 x 28
= 5/3 x ( 3/4 x 7 + 3/7 x 10 + ... + 3/25 x 28 )
= 5/3 x ( 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/25 - 1/28 )
= 5/3 x ( 1/4 - 1/28 )
= 5/3 x 6/28
= 5/14
Tốn công quá !
7 tháng 2 2016
a ) 15 / 90 x 94 + 15 / 94 x 98 + 15 / 98 x102+...+ 15 / 146 x 150
= 15/4 x ( 4/90 x 94 + 4/94 x 98 + ... + 4/ 146 x 150 )
= 15/4 x ( 1/90 - 1/94 + 1/94 - 1/98 + ... + 1/146 - 1/150 )
= 15/4 x ( 1/90 - 1/150 )
= 15/4 x 2/450
= 1/60
b ) 10 / 56 + 10/ 140 + 10 / 260+...+ 10 /1400
= 5/28 + 5/70 + 5/130 + ... + 5/700
= 5/4 x 7 + 5/7 x 10 + 5/10 x 13 + ... + 5 /25 x 28
= 5/3 x ( 3/4 x 7 + 3/7 x 10 + ... + 3/25 x 28 )
= 5/3 x ( 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/25 - 1/28 )
= 5/3 x ( 1/4 - 1/28 )
= 5/3 x 6/28
= 5/14
HC
26 tháng 3 2017
Tk mình đi mọi người mình bị âm nè!
ai tk mình mình tk lại cho!!!
3 tháng 6 2017
a) F = \(\frac{1}{25.27}+\frac{1}{27.29}+\frac{1}{29.31}+...+\frac{1}{73.75}\)
F = \(\frac{1}{2}.\left(\frac{1}{25}-\frac{1}{27}\right)+\frac{1}{2}.\left(\frac{1}{27}-\frac{1}{29}\right)+\frac{1}{2}.\left(\frac{1}{29}-\frac{1}{31}\right)+...+\frac{1}{2}.\left(\frac{1}{73}-\frac{1}{75}\right)\)
F = \(\frac{1}{2}.\left(\frac{1}{25}-\frac{1}{27}+\frac{1}{27}-\frac{1}{29}+\frac{1}{29}-\frac{1}{31}+...+\frac{1}{73}-\frac{1}{75}\right)\)
F = \(\frac{1}{2}.\left(\frac{1}{25}-\frac{1}{75}\right)\)
F = \(\frac{1}{2}.\frac{2}{75}\)
F = \(\frac{1}{75}\)
b) G = \(\frac{15}{90.94}+\frac{15}{94.98}+\frac{15}{98.102}+...+\frac{15}{146.150}\)
G = \(\frac{15}{4}.\frac{4}{90.94}+\frac{15}{4}.\frac{4}{94.98}+\frac{15}{4}.\frac{4}{98.102}+...+\frac{15}{4}.\frac{4}{146.150}\)
G = \(\frac{15}{4}.\left(\frac{1}{90}-\frac{1}{94}\right)+\frac{15}{4}.\left(\frac{1}{94}-\frac{1}{98}\right)+\frac{15}{4}.\left(\frac{1}{98}-\frac{1}{102}\right)+...+\frac{15}{4}.\left(\frac{1}{146}-\frac{1}{150}\right)\)
G = \(\frac{15}{4}.\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+\frac{1}{98}-\frac{1}{102}+...+\frac{1}{146}-\frac{1}{150}\right)\)
G = \(\frac{15}{4}.\left(\frac{1}{90}-\frac{1}{150}\right)\)
G = \(\frac{15}{4}.\frac{1}{225}\)
G = \(\frac{1}{60}\)
3 tháng 6 2017
<br class="Apple-interchange-newline"><div id="inner-editor"></div>12.4 +14.6 +...+198.100
=12 (22.4 +24.6 +...+298.100 )
<br class="Apple-interchange-newline"><div id="inner-editor"></div>=12 (12 −14 +14 −16 +...+198 −1100 )
<br class="Apple-interchange-newline"><div id="inner-editor"></div>=12 (12 −14 +14 −16 +...+198 −1100 )
<br class="Apple-interchange-newline"><div id="inner-editor"></div>=12 (12 −1100 )=12 .49100 =49200
1056 +10140 +10260 +...+101400 =53 (
TK
1
Q
13 tháng 1 2018
\(A=\frac{15}{90.94}+\frac{15}{94.98}+...+\frac{15}{146.150}\)
\(A=15\left(\frac{1}{90.94}+\frac{1}{94.98}+...+\frac{1}{146.150}\right)\)
\(A=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{94}+\frac{1}{94}-\frac{1}{98}+...+\frac{1}{146}-\frac{1}{150}\right)\)
\(A=\frac{15}{4}\left(\frac{1}{90}-\frac{1}{150}\right)\)
\(A=\frac{15}{4}.\frac{1}{225}\)
\(A=\frac{1}{60}\)
\(\dfrac{15}{90\cdot94}+\dfrac{15}{94\cdot98}+\dfrac{15}{98\cdot102}+...+\dfrac{15}{146\cdot150}\)
\(=\dfrac{15}{4}\left(\dfrac{4}{90\cdot94}+\dfrac{4}{94\cdot98}+...+\dfrac{4}{146\cdot150}\right)\)
\(=\dfrac{15}{4}\left(\dfrac{1}{90}-\dfrac{1}{94}+\dfrac{1}{94}-\dfrac{1}{98}+...+\dfrac{1}{146}-\dfrac{1}{150}\right)\)
\(=\dfrac{15}{4}\left(\dfrac{1}{90}-\dfrac{1}{150}\right)=\dfrac{15}{4}\cdot\dfrac{1}{225}=\dfrac{1}{60}\)