\(\left(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\right).120+y:\frac{1}{3}=-4\)

\(\Leftrightarrow\)\(\left(\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\right).120+y:\frac{1}{3}=-4\)

\(\Leftrightarrow\)\(\left(\frac{1}{24}-\frac{1}{30}\right).120+y:\frac{1}{3}=-4\)

\(\Leftrightarrow\)\(1+3y=-4\)

\(\Leftrightarrow\)\(3y=-5\)

\(\Leftrightarrow\)\(y=-\frac{5}{3}\)

Vậy...

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 \(y=-\frac{5}{3}\)

\(\left(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\right).120+y:\frac{1}{3}=-4.\)

\(\Leftrightarrow\left(\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\right).120+y:\frac{1}{3}=-4\)

\(\Leftrightarrow\left(\frac{1}{24}-\frac{1}{30}\right).120+y.\frac{3}{1}=-4\)

\(\Leftrightarrow\frac{1}{120}.120+3y=-4\)

\(\Leftrightarrow1+3y=-4\Leftrightarrow3y=-5\)

\(\Leftrightarrow y=\frac{-5}{3}\)

a)\(\left(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\right).120+x:\frac{1}{3}=-4\)

\(\Rightarrow\left(\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\right).120+x:\frac{1}{3}=-4\)

\(\Rightarrow\left(\frac{1}{24}-\frac{1}{30}\right).120+x:\frac{1}{3}=-4\)

\(\Rightarrow\frac{1}{120}.120+x:\frac{1}{3}=-4\)

\(\Rightarrow1+x:\frac{1}{3}=-4\)

\(\Rightarrow x:\frac{1}{3}=-4-1=-5\)

\(\Rightarrow x=-5.\frac{1}{3}=\frac{-5}{3}\)

b)\(1\frac{3}{5}+\left(\frac{\frac{2}{7}+\frac{2}{17}+\frac{2}{37}}{\frac{5}{7}+\frac{5}{17}+\frac{5}{37}}\right).x=\frac{16}{5}\)

\(\Rightarrow\frac{8}{5}+\left[\frac{2.\left(\frac{1}{7}+\frac{1}{17}+\frac{1}{37}\right)}{5.\left(\frac{1}{7}+\frac{1}{17}+\frac{1}{37}\right)}\right].x=\frac{16}{5}\)

\(\Rightarrow\frac{8}{5}+\frac{2}{5}.x=\frac{16}{5}\)

\(\Rightarrow\frac{2}{5}.x=\frac{16}{5}-\frac{8}{5}=\frac{8}{5}\)

\(\Rightarrow x=\frac{8}{5}:\frac{2}{5}=\frac{8}{5}.\frac{5}{2}=\frac{8}{2}=4\)

\(\Rightarrow x=4\)

y=-5/3 

y=-5/3

y=-5/3

=> 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

\(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}+x:\frac{1}{3}=-4\)

\(\Rightarrow\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}+x\times3=-4\)

\(\Rightarrow\frac{1}{24}-\frac{1}{30}+3x=-4\)

\(\Rightarrow\frac{1}{120}+3x=-4\)

=(1/24-1/25+1/25-1/24+...+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=-4-1/120

x:1/3=-481/120

x=-481/120.1/3

x=-481/360

số to lắm bạn nhé!