a) 

(1/3-1/5)x1/4 = 1/3x1/4-1/5x1/4=1/12-1/20=1/30

(1/3-1/5)x1/4 = 2/15x1/4=1/30

b)

2/5 x 3/7 + 2/5 x 4/7= 6/35 + 8/35 = 14/35 = 2/5

2/5 x 3/7 + 2/5 x 4/7= (3/7+4/7) x 2/5 = 1 x 2/5 = 2/5

a: C1: (1/3-1/5)*1/4

=2/15*1/4=2/60=1/30

C2: (1/3-1/5)*1/4

=1/3*1/4-1/5*1/4

=1/12-1/20=1/30

b: C1: 2/5*3/7+2/5*4/7

=6/35+8/35=14/35=2/5

C2: 2/5*3/7+2/5*4/7

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

=2/5*1=2/5

-3x+(-9)+5x-5=-10

(-3x+5x)+(-9-5)=-10

-2x+(-14)=-10

-2x=-10-(-14)

-2x=24

x=24:(-2)

x=-12. chúc bạn học tối nha

x = 3/4

\(x=\dfrac{5}{8}+\dfrac{1}{8}\)

\(x=\dfrac{6}{8}=\dfrac{3}{4}\)

x = 3/4

Đề bài : Tìm số nguyên x.

|2x-1|+|2+x|+|x+3|=5(x-1)

2x-1+2+x+x+3=5x-5

2x+x+x-5x-1+2+3=-5

-x-1+5=-5

-x-1=(-5)-5

-x-1=-10

-x=(-10)+1

-x=-9

x=9

Vậy x=9.

Không chắc!

\(\left|2x-1\right|+\left|2+x\right|+\left|x+3\right|=5.\left(x-1\right)\left(1\right)\)

+)Ta có VT(1):\(\left|2x-1\right|\ge0;\left|2+x\right|\ge0;\left|x+3\right|\ge0\)

\(\Rightarrow\left|2x-1\right|+\left|2+x\right|+\left|x+3\right|\ge0\)

Mà VT(1)=VP(1)

\(\Rightarrow5.\left(x-1\right)\ge0\)

\(\Rightarrow x-1\ge0\)

\(\Rightarrow x\ge1\)

+)Ta lại có:\(x\ge1\Rightarrow2x-1\ge1\Rightarrow\left|2x-1\right|=2x-1\)(2)

                        \(x\ge1\Rightarrow2+x\ge3\Rightarrow\left|2+x\right|=2+x\)(3)

                       \(x\ge1\Rightarrow x+3\ge4\Rightarrow\left|x+3\right|=x+3\)(4)

+)Từ (2);(3) và (4) thì (1) trở thành:

2x-1+2+x+x+3=5.(x-1)

2x+x+x+2-1+3=5.(x-1)

4x+4              =5.(x-1)

4x+4              =5x-5

4+5                 =5x-4x

9                     =x

\(\Rightarrow\)x                  =9

Vậy x=9

Chúc bn học tốt

=>\(\dfrac{3}{x-5}-\dfrac{y}{3}=\dfrac{1}{6}\)

=>\(\dfrac{9-y\left(x-5\right)}{3\left(x-5\right)}=\dfrac{1}{6}\)

=>9-y(x-5)=1/2(x-5)

=>(x-5)(1/2+y)=9

=>(x-5)(2y+1)=18

=>\(\left(x-5;2y+1\right)\in\left\{\left(18;1\right);\left(-18;-1\right);\left(2;9\right);\left(-2;-9\right);\left(6;3\right);\left(-6;-3\right)\right\}\)

=>\(\left(x,y\right)\in\left\{\left(23;0\right);\left(-13;-1\right);\left(7;4\right);\left(3;-5\right);\left(11;1\right);\left(-1;-2\right)\right\}\)

=14/15*20/21*...*209/210

\(=\dfrac{4\cdot7}{5\cdot6}\cdot\dfrac{5\cdot8}{6\cdot7}\cdot...\cdot\dfrac{19\cdot22}{20\cdot21}\)

\(=\dfrac{4\cdot5\cdot6\cdot...\cdot19}{5\cdot6\cdot7\cdot...\cdot20}\cdot\dfrac{7\cdot8\cdot9\cdot...\cdot22}{6\cdot7\cdot8\cdot...\cdot21}=\dfrac{11}{15}\)