a: Khi x>0 thì A=3x-3x+2=2

Khi x<0 thì A=-3x-3x+2=-6x+2

b: B=4-x-x+5=9-2x

c: TH1: 5/4<x<5/2

A=5-2x-3x+7=12-5x

TH2: x>=5/2

A=2x-5-3x+7=-x+2

d: D=3-5x+|5x-3|

TH1: x>=3/5

D=3-5x+5x-3=0

TH2: x<3/5

D=3-5x+3-5x=6-10x

cảm ơn ạ

8/5

686/65

5/7

can loi giai

1.a,=(54+45+1).113

=100.113

=11300

b,=(3/7+8/14)+(4/9+10/18)

=1+1

=2

2.a,=13/10+1/3

=49/30

b,=12/9.(1/12+1/6)

=12/9.1/4

=1/3

c,=3/4.3/2

=9/8

d,=3/2-1/3

=7/6

1:tính bằng cách thuận tiện nhất:

a)54 x 113 + 45 x 113 + 113

= 54 x 113 + 45 x 113 + 113x1

=113 x(54+45+1)

= 113x100

=1300

 b)3/7 + 4/9 + 8/14 + 10/18

=(3/7+8/14)+(4/9+10/18)

=    1           + 1

=2

a: \(x-\frac25+\frac{7}{12}=\frac12\cdot\frac34\cdot\frac{-9}{16}\)

=>\(x-\frac{24}{60}+\frac{35}{60}=\frac38\cdot\frac{-9}{16}=\frac{-27}{128}\)

=>\(x=-\frac{27}{128}-\frac{11}{60}=\frac{-27\cdot15-11\cdot32}{1920}=-\frac{757}{1920}\)

b: \(\frac49x-\frac12=-\frac59\)

=>\(\frac49x=-\frac59+\frac12=\frac{-10+9}{18}=\frac{-1}{18}\)

=>\(x=-\frac{1}{18}:\frac49=-\frac{1}{18}\cdot\frac94=\frac{-1}{2\cdot4}=-\frac18\)

c: \(-\frac23x+\frac58=\frac{7}{12}\)

=>\(-\frac23x=\frac{7}{12}-\frac58=\frac{14}{24}-\frac{15}{24}=-\frac{1}{24}\)

=>\(x=\frac{1}{24}:\frac23=\frac{1}{24}\cdot\frac32=\frac{1}{8\cdot2}=\frac{1}{16}\)

d: \(\frac25x:\frac73\cdot\frac18=\frac{29}{15}\)

=>\(x\cdot\frac25\cdot\frac37\cdot\frac18=\frac{29}{15}\)

=>\(x\cdot\frac{3}{4\cdot5\cdot7}=\frac{29}{15}\)

=>\(x=\frac{29}{15}:\frac{3}{140}=\frac{29}{15}\cdot\frac{140}{3}=\frac{29\cdot28}{3\cdot3}=\frac{812}{9}\)

3/5+4/6=3/5+2/3=9/15+10/15=19/15

7-1/3=20/3

5x3/8=15/8

12/35:2/5=12/35x5/2=60/70=6/7

\(\dfrac{3}{5}+\dfrac{4}{6}=\dfrac{3}{5}+\dfrac{2}{3}=\dfrac{19}{15}\)
\(7-\dfrac{1}{3}=\dfrac{20}{3}\)
\(5x\dfrac{3}{8}=\dfrac{15}{8}\)
\(\dfrac{12}{35}:\dfrac{2}{5}=\dfrac{12}{35}x\dfrac{5}{2}=\dfrac{6}{7}\)

Bài 2:

Sau 2 giờ con ốc sên bò được:

1/5+1/6=11/30(cây cột)

Sau 2 giờ thì con ốc sên còn phải bò:

1-11/30=19/30(cây cột)

Bài 2: 

Ta có: \(x\left(x-4\right)-x^2+8=0\)

\(\Leftrightarrow x^2-4x-x^2+8=0\)

\(\Leftrightarrow-4x=-8\)

hay x=2

1)=x²-49-x²

=-49

2)=>x²-4x-x²+8=0

=>-4x+8=0

=>-4x=-8

=>x=2

Bài 2: 

a: =>x-35=-23

=>x=12

b: =>|x-8|=13

=>x-8=13 hoặc x-8=-13

=>x=21 hoặc x=-5

Bài 1: 

a: =42-98-42+12-12=-98

b: =10x4x3x(-25)=40x(-25)x3=-1000x3=-3000

1: \(=8+2\sqrt{10}-3\sqrt{10}+\sqrt{10}=8\)