a.

$xy=-21=7.(-3)=(-7).3=3.(-7)=(-3).7=21.(-1)=(-21).1=(-1).21=1(-21)$

Do đó $(x,y)=(7,-3); (-7,3); (3,-7); (-3,7); (21,-1); (-21,1); (-1,21); (1,-21)$

b.

$(x+5)(y-3)=14=1.14=14.1=(-14)(-1)=(-1)(-14)=2.7=7.2=(-2)(-7)=(-7)(-2)$

Do đó:

$(x+5,y-3)=(1,14); (14,1); (-14,-1); (-1,-14); (2,7); (7,2); (-2,-7); (-7,-2)$

Đến đây thì đơn giản rồi.

c.

$x(y-2)=-19$, bạn làm tương tự

d. Tương tự

a: =>2x=-18+5=-13

=>x=-13/2

b: =>3^x-1=81

=>x-1=4

=>x=5

c: =>4(5-x)=24

=>5-x=6

=>x=-1

`2x-15 = 17``

`=> 2x  = 17 + 15`

`=>  2x = 32`

`=>    X = 32 : 2`

`=>    x = 16`

`156 - (x + 61) = 82`

`=>      x + 61  = 156 - 82`

`=>      x + 61   = 74`

`=>       x           = 13`

`2x - 138 = 2^3 . 3^2`

`=>2x - 138 = 72`

`=>  2x        = 210`

`=>   x         = 105`

bài 2:

`23-3x = 8`

`=>  3x = 23 - 8`

`=>   3x = 15`

`=>     x  = 5`

`(x-35) - 120 = 0`

`=>(x-35)      = 120`

`=> x            = 120  +35`

`=>  x           = 155`

`3^x + 2 = 29`

`=>  3^x = 27`

`=>  3^x = 3^3`

`=> x      = 3` 

Bài 1: 

a) Ta có: \(\dfrac{17}{6}-x\left(x-\dfrac{7}{6}\right)=\dfrac{7}{4}\)

\(\Leftrightarrow\dfrac{17}{6}-x^2+\dfrac{7}{6}x-\dfrac{7}{4}=0\)

\(\Leftrightarrow-x^2+\dfrac{7}{6}x+\dfrac{13}{12}=0\)

\(\Leftrightarrow-12x^2+14x+13=0\)

\(\Delta=14^2-4\cdot\left(-12\right)\cdot13=196+624=820\)

Vì Δ>0 nên phương trình có hai nghiệm phân biệt là:

\(\left\{{}\begin{matrix}x_1=\dfrac{14-2\sqrt{205}}{-24}=\dfrac{-7+\sqrt{205}}{12}\\x_2=\dfrac{14+2\sqrt{2015}}{-24}=\dfrac{-7-\sqrt{205}}{12}\end{matrix}\right.\)

b) Ta có: \(\dfrac{3}{35}-\left(\dfrac{3}{5}-x\right)=\dfrac{2}{7}\)

\(\Leftrightarrow\dfrac{3}{5}-x=\dfrac{3}{35}-\dfrac{10}{35}=\dfrac{-7}{35}=\dfrac{-1}{5}\)

hay \(x=\dfrac{3}{5}-\dfrac{-1}{5}=\dfrac{3}{5}+\dfrac{1}{5}=\dfrac{4}{5}\)

ai giúp mik vs

Bài 3: 

a) Ta có: \(2x-3=x+\dfrac{1}{2}\)

\(\Leftrightarrow2x-x=\dfrac{1}{2}+3\)

\(\Leftrightarrow x=\dfrac{7}{2}\)

b) Ta có: \(4x-\left(x+\dfrac{1}{2}\right)=2x-\left(\dfrac{1}{2}-5\right)\)

\(\Leftrightarrow3x-\dfrac{1}{2}-2x+\dfrac{1}{2}-5=0\)

\(\Leftrightarrow x=5\)

a, - ( x + 84 ) + 213 = -16

=> - ( x + 84 ) = -16 - 213

=>  - ( x + 84 ) =-229

=> x + 84 = 229

=> x = 145

b.  x + ( -35 ) = 18

=> x = 18 - ( -35 )

=> x = 18 + 35

=> x = 53

c. -2x - ( - 17 ) = 15

=> -2x = 15 + ( -17)

=> -2x = -2 

=> x = 1

\(a,-\left(x+84\right)+213=-16\)

                             \(x+84=213+16\)

                             \(x+84=229\)

                                        \(x=229-84\) 

                                        \(x=145\)

\(b,x+\left(-35\right)=18\)

                        \(x=18+35\)

                        \(x=53\)

\(c,-2x-\left(-17\right)=15\)

               \(-2x+17=15\)

                              \(2x=17-15\)         

                              \(2x=2\)

                                 \(x=1\)

a) 78 - x = 90

x = 78 - 90

x = -12

b) 15 + 2x = 5¹⁰ : 5⁸

15 + 2x = 5²

15 + 2x = 25

2x = 25 - 15

2x = 10

x = 10 : 2

x = 5

c) 48 : x + 17 = -33

48 : x + 17 = -33 - 17

48 : x = -50

x = 48 : (-50)

x = -24/25

d) Do x ⋮ 15 và x ⋮ 20

⇒ x ∈ BC(15; 20)

Ta có:

15 = 3.5

20 = 2².5

⇒ BCNN(15; 20) = 2².3.5 = 60

⇒ x ∈ BC(15; 20) = {0; 60; 120; ...}

Mà 50 < x < 70

⇒ x = 60

X + (- 35 ) = 18

X - 35 = 18

       X = 18 + 35

       X = 53

Vậy X = 53

- 2x -(- 17)= 15

- 2x + 17 = 15

- 2x = 15 - 17

- 2x = - 2

    x = - 2 : ( - 2 )

    x = 1

Vậy x = 1

1) x+ (-35)=18

<=> x-35=18

<=> x=53

2) -2x-(-17)=15

<=> -2x+17=15

<=> -2x=-2

<=> x=1

a)X + (- 35 ) = 18

x = 18 + 35

x = 53

b)- 2x -(- 17)= 15

-2x = 15 - 17

-2x = -2

x = 1

hok tốt!!!

Giải:

a) \(\left(x-1\right)\left(y+2\right)=7\) 

\(\Rightarrow\left(x-1\right)\) và \(\left(y+2\right)\inƯ\left(7\right)=\left\{\pm1;\pm7\right\}\) 

Ta có bảng giá trị:

Vậy \(\left(x;y\right)=\left\{\left(-6;-3\right);\left(0;-9\right);\left(2;5\right);\left(8;-1\right)\right\}\) 

b) \(\left(x-2\right)\left(3y+1\right)=17\) 

\(\Rightarrow\left(x-2\right)\) và \(\left(3y+1\right)\inƯ\left(17\right)=\left\{\pm1;\pm17\right\}\) 

Ta có bảng giá trị:

Vậy \(\left(x;y\right)=\left\{\left(1;-6\right);\left(19;0\right)\right\}\)

Ko ghi lại đề nhé 

a) \(TH1\left[{}\begin{matrix}x-1=1\\y+2=7\end{matrix}\right.=>\left[{}\begin{matrix}x=2\\y=5\end{matrix}\right.\)

\(TH2:\left[{}\begin{matrix}x-1=-1\\y+2=-7\end{matrix}\right.=>\left[{}\begin{matrix}x=0\\y=-9\end{matrix}\right.\)

\(TH3:\left[{}\begin{matrix}x-1=7\\y+2=1\end{matrix}\right.=>\left[{}\begin{matrix}x=8\\y=-1\end{matrix}\right.\)

\(TH4:\left[{}\begin{matrix}x-1=-7\\y+2=-1\end{matrix}\right.=>\left[{}\begin{matrix}x=-6\\y=-3\end{matrix}\right.\)

b) \(TH1:\left[{}\begin{matrix}x-2=1\\3y+1=17\end{matrix}\right.=>\left[{}\begin{matrix}x=3\\y=\dfrac{16}{3}\end{matrix}\right.=>Loại\)

\(TH2:\left[{}\begin{matrix}x-2=-1\\3y+1=-17\end{matrix}\right.=>\left[{}\begin{matrix}x=1\\y=-6\end{matrix}\right.Chọn\)

\(TH3:\left[{}\begin{matrix}x-2=17\\3y+1=1\end{matrix}\right.=>\left[{}\begin{matrix}x=19\\y=0\end{matrix}\right.=>Chọn\)

\(TH4:\left[{}\begin{matrix}x-2=-17\\3y+1=-1\end{matrix}\right.=>\left[{}\begin{matrix}x=-15\\y=\dfrac{-2}{3}\end{matrix}\right.=>Loại\)

Bạn tự kết luận hộ mk nha

Bài 2:

a: -2*(-27)=54

6*9=54

=>Hai phân số này bằng nhau

b: -1/-5=1/5=5/25<>4/25

Bài 3:

a: =>16/x=-4/5

=>x=-20

b: =>(x+7)/15=-2/3

=>x+7=-10

=>x=-17

a) \(\dfrac{-2}{9}\) và \(\dfrac{6}{-27}\)

\(\dfrac{6}{-27}=\dfrac{6:\left(-3\right)}{\left(-27\right):\left(-3\right)}=\dfrac{-2}{9}\)

Vậy \(\dfrac{-2}{9}=\dfrac{6}{-27}\)

b) \(\dfrac{-1}{-5}\) và \(\dfrac{4}{25}\)

\(\dfrac{-1}{-5}=\dfrac{\left(-1\right).\left(-5\right)}{\left(-5\right).\left(-5\right)}=\dfrac{5}{25}\)

Do \(5\ne4\Rightarrow\dfrac{5}{25}\ne\dfrac{4}{25}\)

Vậy \(\dfrac{-1}{-5}\ne\dfrac{4}{25}\)

Bài 3

a) \(\dfrac{-28}{35}=\dfrac{16}{x}\)

\(x=\dfrac{35.16}{-28}\)

\(x=-20\)

b) \(\dfrac{x+7}{15}=\dfrac{-24}{36}\)

\(\left(x+7\right).36=15.\left(-24\right)\)

\(36x+252=-360\)

\(36x=-360-252\)

\(36x=-612\)

\(x=\dfrac{-612}{36}\)

\(x=-17\)