\(\dfrac{2x^2-x}{x-1}+\dfrac{x+1}{1-x}+\dfrac{2-x^2}{x-1}.\left(x\ne1\right).\)

\(\dfrac{2x^2-x-x-1+2-x^2}{x-1}=\dfrac{x^2-2x+1}{x-1}=\dfrac{\left(x-1\right)^2}{x-1}=x-1.\)

1/ 5(-2-1)-3(2-5)

=5.1-3.(-3)

=5-(-9)

=14

2/ 15(2-1)-3(4+2)

=15.1-3.8

=15-24

=-9

3/ -3(7-2)+5(4-3)

=-3.5+5.1

=-15+5

=-10

tick len 460 tui giai cho

1/ -6

2/ 1

3/ 20

cũng dễ mà

mk ghi kết quả thui ha

a) = 250

b) = -27

c) = -3

tick nhé

a) =250        b) =-27          c) =-3

=5x2+7x3=31

\(\text{5*2+7*3}\)

\(=10+21\)

\(=31\)

\(a.\dfrac{4}{5}+x=\dfrac{8}{10}\\ \Rightarrow x=\dfrac{8}{10}-\dfrac{4}{5}\\ \Rightarrow x=\dfrac{8}{10}-\dfrac{8}{10}\\ \Rightarrow x=0\\ b.\dfrac{1}{7}-7\left(\dfrac{2}{3}-x\right)=-\dfrac{4}{7}\\ \Rightarrow\dfrac{1}{7}-\dfrac{14}{3}+7x=-\dfrac{4}{7}\\ \Rightarrow-\dfrac{95}{21}+7x=-\dfrac{4}{7}\\\Rightarrow7x=\dfrac{83}{21}\\ \Rightarrow x=\dfrac{83}{147} \)

`a)4/5+x=8/10`

`=>x=8/10-4/5`

`=>x=4/5-4/5`

`=>x=0`

Vậy `x=0`

__

`b)1/7-7(2/3-x)=-4/7`

`=>7(2/3-x)=1/7-(-4/7)`

`=>7(2/3-x)=1/7+4/7`

`=>7(2/3-x)=5/7`

`=>2/3-x=5/7:7`

`=>2/3-x=5/7xx1/7`

`=>2/3-x=5/49`

`=>x=2/3-5/49`

`=>x=98/147-15/147`

`=>x=83/147`

Vậy `x=83/147`

a)\(\left(x+3\right)\times5+1=20\Leftrightarrow5x+15=19\)

\(\Leftrightarrow5x=4\Leftrightarrow x=\frac{4}{5}\)

b)sai đề

c)\(2\frac{3}{7}\times x+1\frac{5}{4}=5\frac{3}{42}\)\(\Leftrightarrow\frac{17}{7}\times x+\frac{9}{4}=\frac{71}{14}\) \(\Leftrightarrow\frac{17}{7}\times x+\frac{63}{28}=\frac{142}{28}\)

\(\Leftrightarrow\frac{17}{7}\times x=\frac{79}{28}\Leftrightarrow x=\frac{17}{7}:\frac{79}{28}\) \(\Leftrightarrow x=\frac{17}{7}\times\frac{28}{79}\Leftrightarrow x=\frac{476}{553}=\frac{68}{79}\)

d)\(10\frac{2}{3}-x:\frac{6}{7}=8\frac{1}{3}-6\frac{2}{7}\Leftrightarrow\frac{32}{3}-x:\frac{6}{7}=\frac{25}{3}-\frac{44}{7}\) \(\Leftrightarrow\frac{224}{21}-x:\frac{6}{7}=\frac{75}{21}-\frac{132}{21}\Leftrightarrow-\frac{57}{21}-\frac{224}{21}\)

\(\Leftrightarrow-x:\frac{6}{7}=-\frac{281}{21}\Leftrightarrow-x=-\frac{281}{21}\times\frac{6}{7}\) \(\Leftrightarrow-x=-\frac{1686}{147}\Leftrightarrow x=\frac{562}{49}=11\frac{23}{49}\)

Bài 1: 

\(=\dfrac{-1}{2}+\dfrac{3}{5}-\dfrac{1}{9}+\dfrac{1}{131}+\dfrac{2}{7}+\dfrac{4}{35}-\dfrac{7}{18}\)

\(=\left(-\dfrac{1}{2}-\dfrac{1}{9}-\dfrac{7}{18}\right)+\left(\dfrac{3}{5}+\dfrac{2}{7}+\dfrac{4}{35}\right)+\dfrac{1}{131}\)

\(=\dfrac{-9-2-7}{18}+\dfrac{21+10+4}{35}+\dfrac{1}{131}\)

=1/131

Bài 2:

b: \(B=\dfrac{1}{99}-\left(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+...+\dfrac{1}{98\cdot99}\right)\)

\(=\dfrac{1}{99}-\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{98}-\dfrac{1}{99}\right)\)

\(=\dfrac{1}{99}-\dfrac{98}{99}=-\dfrac{97}{99}\)