Bài 2: 

a: \(\left(6x-39\right):7=3\)

\(\Leftrightarrow6x-39=21\)

hay x=10

Bài 1:

a: \(\frac{x}{7}-\frac12=\frac{1}{y+1}\)

=>\(\frac{2x-7}{14}=\frac{1}{y+1}\)

=>(2x-7)(y+1)=14

mà 2x-7 lẻ

nên (2x-7;y+1)∈{(1;14);(-1;-14);(7;2);(-7;-2)}

=>(2x;y)∈{(8;13);(6;-15);(14;1);(0;-3)}

=>(x;y)∈{(4;13);(3;-15);(7;1);(0;-3)}

b: \(\frac{5}{x}-\frac{y}{4}=\frac18\)

=>\(\frac{5}{x}=\frac{y}{4}+\frac18=\frac{2y+1}{8}\)

=>x(2y+1)=40

mà 2y+1 lẻ

nên (x;2y+1)∈{(40;1);(-40;-1);(8;5);(-8;-5)}

=>(x;2y)∈{(40;0);(-40;-2);(8;4);(-8;-6)}

=>(x;y)∈{(40;0);(-40;-1);(8;2);(-8;-3)}

c: \(\frac{2}{y}-\frac{1}{x}=\frac{8}{xy}+1\)

=>\(\frac{2x-y}{xy}=\frac{8+xy}{xy}\)

=>xy+8=2x-y

=>xy-2x+y+8=0

=>x(y-2)+y-2+10=0

=>(x+1)(y-2)=-10

=>(x+1;y-2)∈{(1;-10);(-10;1);(-1;10);(10;-1);(2;-5);(-5;2);(-2;5);(5;-2)}

=>(x;y)∈{(0;-8);(-11;3);(-2;12);(9;1);(1;-3);(-6;4);(-3;7);(4;0)}

mà y<>0 và x<>0

nên (x;y)∈{(-11;3);(-2;12);(9;1);(1;-3);(-6;4);(-3;7)}

a)(126-14)x0

=0

b)124+60

=184

a = 0 

b = 184

Bài 1:

a) x - 32 + 25 = 12 x 2

    x- 32  +25 = 24

    x -32         = -1

    x               = 31

b) 24 + x - 3 = 21

   24+x         = 24

        x          = 0

c) x * 10 : 2 = 40

    x *10       = 80

    x             = 8

Bài 2:

a) 123 - 82 x 6= 123- 492= -369

b) 458 - 125 + 23= 333+23 = 356

c) 325 + 125 x 125 x 325= 325 + 5 078 450

 Cái này giống như bài lớp 6 ý.

Bài 1 : Tìm x

a) x - 32 + 25 = 12 x 2

    x - 32 + 25 = 24

    x - 32         = 24 - 25

     x - 32        = ( - 1 )

      x             = ( -1 ) + 32

      x           = 31

b) 24 + x - 3 = 21

   24 + x       = 21 + 3

   24 + x       = 24

           x       = 24 - 24

           x        = 0

c) x * 10 : 2 = 40

    x * 10      = 40 x 2

    x * 10      = 80

    x             = 80 : 10

    x             = 8

Bài 2: Tính giá trị của biểu thức 

a) 123 - 82 x 6

    123 - 492

    -369

b) 458 - 125 + 23

   333 + 23

   356

c) 325 + 125 x 125 x 325

    325 + 5078125

    5078450

Các bạn làm nhanh hộ mình, mình đang cần gấp😊

1.8100

2. 34 x 18 + 18 x 66

= 18 x ( 34 + 66)

= 18 x 100 = 1800

3. X × ( 8 +  12) =  160 + 20 × 12

= X x 20 = 160 + 240

= X x 20 = 400

X = 400 : 20 = 20

4. X x 12 - X x 2 = 2020

(12 - 2) x X = 2020

10 x X = 2020

X = 2020 : 10 = 202

1.8100

2. 34 x 18 + 18 x 66

= 18 x ( 34 + 66)

= 18 x 100 = 1800

3. X × ( 8 +  12) =  160 + 20 × 12

= X x 20 = 160 + 240

= X x 20 = 400

X = 400 : 20 = 20

4. X x 12 - X x 2 = 2020

(12 - 2) x X = 2020

10 x X = 2020

X = 2020 : 10 = 202

\(325-5\left[4^3-\left(27-5^2\right)\cdot1^{18}\right]\\ =325-5\left[64-\left(27-25\right)\cdot1\right]\\ =325-5\left(64-2\right)=325-5\cdot62=325-310=15\)

\(325-5\left[4^3-\left(27-5^2\right).1^{18}\right]\)

\(=325-5\left[64-\left(27-25\right).1\right]\)

\(=325-5\left[64-2.1\right]\)

\(=325-5.62\)

\(=325-124\)

\(=201\)

\(\left(325-317\right)^3-2\left(x-1\right)=2^{18}:8^2\)

\(8^3-2x+2=2^{18}:\left(2^3\right)^2\)

\(512-2x+2=2^{18}:2^6\)

\(514-2x=2^{18-6}\)

\(514-2x=2^{12}\)

\(-2x=4096-514\)

\(-2x=3582\)

\(x=-1791\)

giúp mình vs các bạn ơi

1: \(=\dfrac{-\left[\left(x+5\right)^2-9\right]}{\left(x+2\right)^2}=\dfrac{-\left(x+5-3\right)\left(x+5+3\right)}{\left(x+2\right)^2}\)

\(=\dfrac{-\left(x+2\right)\left(x+8\right)}{\left(x+2\right)^2}=\dfrac{-\left(x+8\right)}{x+2}\)

2: \(=\dfrac{2x\left(x^2-4x+16\right)}{\left(x+4\right)\left(x^2-4x+16\right)}=\dfrac{2x}{x+4}\)

3: \(=\dfrac{5x\left(x^2+1\right)}{\left(x^2-1\right)\left(x^2+1\right)}=\dfrac{5x}{x^2-1}\)

4: \(=\dfrac{3\left(x^2-4x+4\right)}{x\left(x^3-8\right)}=\dfrac{3\left(x-2\right)^2}{x\left(x-2\right)\left(x^2+2x+4\right)}\)

\(=\dfrac{3\left(x-2\right)}{x\left(x^2+2x+4\right)}\)

5: \(=\dfrac{2a\left(a-b\right)}{a\left(c+d\right)-b\left(c+d\right)}=\dfrac{2a\left(a-b\right)}{\left(c+d\right)\left(a-b\right)}=\dfrac{2a}{c+d}\)

6: \(=\dfrac{x\left(x-y\right)}{\left(x-y\right)\left(x+y\right)}\cdot\left(-1\right)=\dfrac{-x}{x+y}\)

7: \(=\dfrac{2\left(1-a\right)}{-\left(1-a^3\right)}=\dfrac{-2\left(1-a\right)}{\left(1-a\right)\left(1+a+a^2\right)}=-\dfrac{2}{1+a+a^2}\)

8: \(=\dfrac{x^4\left(x^3-1\right)}{\left(x^3-1\right)\left(x^3+1\right)}=\dfrac{x^4}{x^3+1}\)

9: \(=\dfrac{\left(x+2-x+2\right)\left(x+2+x-2\right)}{16x}=\dfrac{4\cdot2x}{16x}=\dfrac{1}{2}\)

10: \(=\dfrac{0.5\left(49x^2-y^2\right)}{0.5x\left(7x-y\right)}=\dfrac{1}{x}\cdot\dfrac{\left(7x-y\right)\left(7x+y\right)}{7x-y}\)

\(=\dfrac{7x+y}{x}\)

a)15/8+3/4-5/12

=45+18-10/24

=53/24

b)11/24.12/33+5/6

=11.12/12.2.11.3+5/6

=1/6+5/6

=6/6=1

c)15/8+7/24:5/8

=15/8+7/24.8/5

=15/8+7.8/3.8.5

=15/8+7/15

=đề sai, nếu đúng thì như này

=8/15+7/15

=15/15=1

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