\(\dfrac{6}{x}+\dfrac{1}{2}=2\\ \dfrac{6}{x}=2-\dfrac{1}{2}\\ \dfrac{6}{x}=\dfrac{4}{2}-\dfrac{1}{2}\\ \dfrac{6}{x}=\dfrac{3}{2}\\ x=6:\dfrac{3}{2}\\ x=\dfrac{6x2}{3}\\ x=4\)

Đủ chi tiết chưa nhỉ ??

x=4

 6/x =2-1/2

6x=2/1 -1/2

6/x=3/2

x=1/4

vậy x =1/4

chúc em học tốt

\(\dfrac{25}{30}=\dfrac{5}{7};\dfrac{9}{15}=\dfrac{3}{5};\dfrac{6}{10}=\dfrac{3}{5};\dfrac{10}{12}=\dfrac{5}{6}\)

tự xem cái nào giống

a) \(\dfrac{3}{5};\dfrac{5}{6}\) : phân số tối giản
\(\dfrac{25}{30}=\dfrac{25:5}{30:5}=\dfrac{5}{6}\)
\(\dfrac{9}{15}=\dfrac{9:3}{15:3}=\dfrac{3}{5}\)
\(\dfrac{10}{12}=\dfrac{10:2}{12:2}=\dfrac{5}{6}\)
\(\dfrac{6}{10}=\dfrac{6:2}{10:2}=\dfrac{3}{5}\)
b) \(\dfrac{3}{5}=\dfrac{9}{15}=\dfrac{6}{10}\) ; \(\dfrac{5}{6}=\dfrac{25}{30}=\dfrac{10}{12}\)

Bài 6:

\(max_{x-y}=max_x-min_y=11-\left(-89\right)=100\\ min_{x-y}=min_x-max_y=-2-1=-3\)

Bài 7:

\(\Leftrightarrow2\left(a+b+c\right)=11-3-2=6\\ \Leftrightarrow a+b+c=3\\ \Leftrightarrow\left\{{}\begin{matrix}a=3-\left(b+c\right)=6\\b=11-a=5\\c=-3-b=-8\end{matrix}\right.\)

Bài 7:

Ta có:

\(\left(a+b\right)+\left(b+c\right)+\left(a+c\right)=11+\left(-3\right)+\left(-2\right)\\ \Rightarrow2\left(a+b+c\right)=6\\ \Rightarrow a+b+c=3\)

\(\Rightarrow\left\{{}\begin{matrix}a=\left(a+b+c\right)-\left(b+c\right)=3-\left(-3\right)=6\\b=\left(a+b+c\right)-\left(a+c\right)=3-\left(-2\right)=5\\c=\left(a+b+c\right)-\left(a+b\right)=3-11=-8\end{matrix}\right.\)

Bài 7

Ta có: \(a+b=11;b+c=-3;a+c=-2\)

\(\Rightarrow a+b+b+c+c+a=11+\left(-3\right)+\left(-2\right)\)

\(\Rightarrow2\left(a+b+c\right)=6\)

\(\Rightarrow a+b+c=3\)

Thay a+b=11 vào a+b+c=3 ta có:

\(11+c=3\Rightarrow c=-8\)

Thay b+c=-3 vào a+b+c=3 ta có:

\(\Rightarrow a+\left(-3\right)=3\Rightarrow a=6\)

Thay a=6 và a+b=11 ta có:

\(6+b=11\Rightarrow b=5\)

\(C=\dfrac{2}{5}+\dfrac{2}{45}+...+\dfrac{2}{6885}\)

\(=\dfrac{1}{2}\left(\dfrac{4}{1\cdot5}+\dfrac{4}{5\cdot9}+\dfrac{4}{9\cdot13}+...+\dfrac{4}{81\cdot85}\right)\)

\(=\dfrac{1}{2}\left(1-\dfrac{1}{85}\right)\)

\(=\dfrac{1}{2}\cdot\dfrac{84}{85}=\dfrac{42}{85}\)

\(\dfrac{41}{66}\)

\(\dfrac{67}{30}\)

a, =5/11+1/6=41/66

b, = 5/2-4/15=67/30

a. 41/66

b. 67/30

Bài 2:

a. $=124-52.124+124.47=124(1-52+47)=124(48-52)=124.(-4)=-496$

b. $=55(-78)+13(-78)-65(-78)=(-78)(55+13-65)=(-78).3=-234$

c. $=100(-47)+53(-100)=100(-47)+(-53).100=100[(-47)+(-53)]=100.(-100)=-10000$

d. $=25.75-25.49.3-75.25+75.49$

$=25.75-49.75-75.25+75.49=(25.75-75.25)+(75.49-49.75)=0+0=0$

Bài 3:
a. Ta nhớ quy tắc âm * âm = dương nên:

$(-18)(-13)>0$

$(-15)(-17)>0$

$\Rightarrow (-18)(-13)> (-15)(-17)$ (đpcm)

b. 

$(-1)(-2)>0$

$(-3)(-4)>0$

$.....$

$(-17)(-18)>0$

$-19<0$

$\Rightarrow (-1)(-2)...(-18)(-19)<0$

Bài 2
a)-7<x<6
x=-6;-5;-4;-3;-2;-1;0;1;2;3;4;5.
b)4>x>-5
x=3;2;1;0;-1;-2;-3;-4
 

Bài 5:

d: 8-x=12

nên x=-4

e: x+16=7

nên x=-9