LB
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K
Khách
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HT
2
30 tháng 7 2018
\((\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}).120+y:\frac{1}{3}=-4\)
Ta có: \(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\)
\(=\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\)
\(=\frac{1}{24}-\frac{1}{30}\)
\(=\frac{1}{120}\)
Thay vào ta có: \(\frac{1}{120}.120+y:\frac{1}{3}=-4\)
\(\implies 1+y:\frac{1}{3}=-4\)
\(\implies y:\frac{1}{3}=-5\)
\(\implies y=-5.\frac{1}{3}\)
\(\implies y=\frac{-5}{3}\). Vậy \(y=\frac{-5}{3}\)
~ Học tốt a~
30 tháng 7 2018
\(\left(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\right).120+y:\frac{1}{3}=-4\)
\(\Rightarrow\left(\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\right).120+y:\frac{1}{3}=-4\)
\(\Rightarrow\left(\frac{1}{24}-\frac{1}{30}\right).120+y:\frac{1}{3}=-4\)
\(\Rightarrow\frac{1}{120}.120+y:\frac{1}{3}=-4\)
\(\Rightarrow1+y:\frac{1}{3}=-4\)
\(\Rightarrow y:\frac{1}{3}=-4-1\)
\(\Rightarrow y:\frac{1}{3}=-5\)
\(\Rightarrow y=-5.\frac{1}{3}\)
\(\Rightarrow y=\frac{-5}{3}\)
Vậy \(y=\frac{-5}{3}\)
_Chúc bạn học tốt_
JN
0
LL
2
23 tháng 6 2016
(1/24.25 + 1/25.26 + ... + 1/29.30) . 120 + x : 1/3 = -4
(1/24 - 1/25 + 1/25 - 1/26 + ... + 1/29 - 1/30) . 120 + x . 3 = -4
(1/24 - 1/30) . 120 + x . 3 = -4
(5/120 - 4/120) + x . 3 = -4
=> 1/120 . 120 + x . 3 = -4
=> 1 + x . 3 = -4
=> x . 3 = -4 - 1
=> x . 3 = -5
=> x = -5/3
Vậy x = -5/3
NM
5
KT
11 tháng 7 2018
\(\left(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\right).120+y:\frac{1}{3}=-4\)
\(\Leftrightarrow\)\(\left(\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\right).120+y:\frac{1}{3}=-4\)
\(\Leftrightarrow\)\(\left(\frac{1}{24}-\frac{1}{30}\right).120+y:\frac{1}{3}=-4\)
\(\Leftrightarrow\)\(1+3y=-4\)
\(\Leftrightarrow\)\(3y=-5\)
\(\Leftrightarrow\)\(y=-\frac{5}{3}\)
Vậy...
AK
11 tháng 7 2018
Ta có :
\(\left(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\right).120+y:\frac{1}{3}=-4\)
\(\Rightarrow\left(\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\right).120+y.3=-4\)
\(\Rightarrow\left(\frac{1}{24}-\frac{1}{30}\right).120+y.3=-4\)
\(\Rightarrow\left(\frac{5}{120}-\frac{4}{120}\right).120+y.3=-4\)
\(\Rightarrow\frac{1}{120}.120+y.3=-4\)
\(\Rightarrow1+y.3=-4\)
\(\Rightarrow3y=-4-1\)
\(\Rightarrow3y=-5\)
\(\Rightarrow y=-\frac{5}{3}\)
Vậy \(y=-\frac{5}{3}\)
AH
Akai Haruma
Giáo viên
8 tháng 6 2021
Lời giải:
\(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}=\frac{25-24}{24.25}+\frac{26-25}{25.26}+...+\frac{30-29}{29.30}\)
\(=\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\)
\(=\frac{1}{24}-\frac{1}{30}=\frac{1}{120}\)
Vậy:
\(\frac{1}{120}.120+x:\frac{1}{3}=-4\)
\(1+x:\frac{1}{3}=-4\)
\(x:\frac{1}{3}=-5\)
\(x=-15\)
10 tháng 6 2021
\(\left(\dfrac{1}{24.25}+\dfrac{1}{25.26}+...+\dfrac{1}{29.30}\right).120+x:\dfrac{1}{3}=-4\)
\(\left(\dfrac{1}{24}-\dfrac{1}{25}+\dfrac{1}{25}-\dfrac{1}{26}+...+\dfrac{1}{29}-\dfrac{1}{30}\right).120+x:\dfrac{1}{3}=-4\)
\(\left(\dfrac{1}{24}-\dfrac{1}{30}\right).120+x:\dfrac{1}{3}=-4\)
\(\dfrac{1}{120}.120+x:\dfrac{1}{3}=-4\)
\(1+x:\dfrac{1}{3}=-4\)
\(x:\dfrac{1}{3}=-4-1\)
\(x:\dfrac{1}{3}=-5\)
\(x=-5.\dfrac{1}{3}\)
\(x=\dfrac{-5}{3}\)
KD
3
Q
17 tháng 4 2018
=> 1/24 - 1/25 + 1/25 - 1/ 26 + .... + 1/29 - 1/30 + x : 1/3 = -4
=> 1/24 - 1/30 + x : 1/3 = - 4
=> 1/ 120 + x : 1/3 = -4
=> x : 1/3 = 481/120
=> x = 481/360
Vậy x = 481/360
17 tháng 4 2018
\(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}+x:\frac{1}{3}=-4\)
\(\Rightarrow\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}+x\times3=-4\)
\(\Rightarrow\frac{1}{24}-\frac{1}{30}+3x=-4\)
\(\Rightarrow\frac{1}{120}+3x=-4\)
30 tháng 7 2018
\(a) \frac{4}{5}.x=\frac{8}{35}\)
\(\implies x= \frac{8}{35}:\frac{4}{5}\)
\(\implies x=\frac{8}{35}.\frac{5}{4}\)
\(\implies x=\frac{2}{7}\). Vậy \(x=\frac{2}{7}\)
\(b) \frac{3}{5}x-\frac{1}{2}=\frac{1}{7}\)
\(\implies \frac{3}{5}x=\frac{1}{7}+\frac{1}{2}\)
\(\implies \frac{3}{5}x=\frac{9}{14}\)
\(\implies x=\frac{9}{14}:\frac{3}{5}\)
\(\implies x=\frac{9}{14}.\frac{5}{3} \)
\(\implies x=\frac{15}{14}\). Vậy \(x=\frac{15}{14}\)
\(c) x-25\% x=0,5\)
\(\implies 75\% x=0,5\)
\(\implies \frac{3}{4}x=\frac{1}{2}\)
\(\implies x=\frac{1}{2}:\frac{3}{4}\)
\(\implies x=\frac{1}{2}.\frac{4}{3}\)
\(\implies x=\frac{2}{3}\). Vậy \(x=\frac{2}{3}\)
\(d) (\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}).120+x:\frac{1}{3}=-4\)
Có: \(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\)
\(=\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\)
\(=\frac{1}{24}-\frac{1}{30}\)
\(=\frac{1}{120}\)
Thay vào ta có: \(\frac{1}{120}.120+x:\frac{1}{3}=-4\)
\(\implies 1+x:\frac{1}{3}=-4\)
\(\implies x:\frac{1}{3}=-5\)
\(\implies x=-5.\frac{1}{3}\)
\(\implies x=\frac{-5}{3}\). Vậy \(x=\frac{-5}{3}\)
~ Hok tốt a~
30 tháng 7 2018
\(\frac{4}{5}.x=\frac{8}{35}\) \(\frac{3}{5}x-\frac{1}{2}=\frac{1}{7}\)
\(x=\frac{8}{35}:\frac{4}{5}\) \(\frac{3}{5}x=\frac{1}{7}+\frac{1}{2}\)
\(x=\frac{8}{35}.\frac{5}{4}\) \(\frac{3}{5}x=\frac{9}{14}\)
\(x=\frac{2}{7}\) \(x=\frac{9}{14}:\frac{3}{5}\)
Vậy \(x=\frac{2}{7}\) \(x=\frac{9}{14}.\frac{5}{3}\)
\(x-25\%x=0.5\) \(x=\frac{15}{14}\)
\(x-\frac{1}{4}x=\frac{1}{2}\) Vậy \(x=\frac{15}{14}\)
\(x\left(1-\frac{1}{4}\right)=\frac{1}{2}\) \(\left(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\right).120+x:\frac{1}{3}=-4\)
\(x=\frac{1}{2}:\frac{3}{4}\) \(\left(\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\right).120+x:\frac{1}{3}=-4\) \(x=\frac{2}{3}\) \(\left(\frac{1}{24}-\frac{1}{30}\right).120+x:\frac{1}{3}=-4\)
Vậy \(x=\frac{2}{3}\) \(\frac{1}{120}.120+x:\frac{1}{3}=-4\)
\(1+x:\frac{1}{3}=-4\)
\(x:\frac{1}{3}=\left(-4\right)-1\)
\(x:\frac{1}{3}=-5\)
\(x=\left(-5\right).\frac{1}{3}\)
\(x=-\frac{5}{3}\)
Vậy \(x=-\frac{5}{3}\)
11 tháng 7 2016
\(\frac{1}{24\cdot25}+\frac{1}{25\cdot26}+...+\frac{1}{29\cdot30}\)
\(=\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\)
\(=\frac{1}{24}-\frac{1}{30}\)
\(=\frac{1}{120.}\)
11 tháng 7 2016
\(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\)
\(=\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\)
\(=\frac{1}{24}-\frac{1}{30}\)
\(=\frac{1}{120}\)
Ủng hộ mk nha ^_-
\(\frac{1}{24.25}+\frac{1}{25.26}+\frac{1}{26.27}+...+\frac{1}{29.30}+y:\frac{1}{3}=-4\)
\(\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+\frac{1}{26}-\frac{1}{27}+...+\frac{1}{29}-\frac{1}{30}+y:\frac{1}{3}=-4\)
\(\frac{1}{24}-\frac{1}{30}+3y=-4\)
\(\frac{1}{120}+3y=-4\)
\(3y=-4-\frac{1}{120}\)
\(3y=-\frac{481}{120}\)
\(y=-\frac{481}{120}:3\)
\(y=-\frac{481}{360}\)