Tương tự 3. HS tự làm.

Bài 3:
a) 11 - (15 + 11) = x - (25 - 9)
=> 11 - 15 - 11 = x - 25 + 9
=> x = 9 - 25 + 15
=> x =       -1
b) 2 - x = 17 - (-5)
=> 2 - x = 17 + 5
=>    -x = 17 + 5 - 2
=>    -x = 20
=>     x = -20
c) x - 12 = (-9) - 15
=> x - 12 = -9 - 15
=> x        = -9 - 15 + 12
=> x        =        -12
d) IxI - 7 = 9
=> IxI = 9 + 7
=> IxI = 16
=> x = 16      hay     x = -16
e) 9 - 25 = (7 - x) - (25 + 7)
=> 9 - 25 = 7 - x - 25 - 7
=>  x = 7 - 7 - 25 + 25 - 9
=>  x = -9

Bài 4:
a) 25 . 46 + 54 . 25
= 25(46 + 54)
= 25.100
= 2500
b) 1200 : 25
= (25.48) : 25
= 25:25 . 48
=     1.48
=        48
c) 1356 - 998
= 1356 + 2 - 998 - 2
= 1358 - 1000
=        358
d) 117 + 57 - 17
=  117 - 17 + 57
=       100 + 57
=         157

Bài 5:
a) 3⁴ . 3¹⁵
= 3^{4 + 15}
= 3¹⁹
b) 8⁸ : 8⁸
= 8^{8 - 8}
= 8⁰
= 1
c) 100 - [120 - (15 - 5)² ]
=  100 - (120 - 10²⁾
=  100 - (120 - 100)
=  100 - 120 + 100
=            80

Bài 3 : 

a, 11 - ( 15 + 11 ) = x - ( 25 - 9 )

               11 - 26 = x - 16 

                   - 15 = x - 16 

                        x = - 15 + 16 

                        x = 1

b, 2 - x = 17 - ( - 5 )

    2 - x = 22

         x = 2 - 22 

         x = - 20 

c, x - 12 = - 9 - 15 

    x - 12 = - 24 

            x = - 24 + 12 

            x = - 12 

d, | x | - 7 = 9 

    | x | = 9 + 7 

     | x | = 16

     x = 16 hoặc - 16

e, 9 - 25 = ( 7 - x ) - ( 25 + 7 )

      - 16 = 7 - x - 32

        x = 7 - 32 + 16 

        x = - 9

Bài 4 : 

25 x 46 + 54 x 25 

= 25 x ( 46 + 54 )

= 25 x 100

= 2500

b, 1200 : 25

= 12 x 100 : 25 

= 12 x 4 

= 48 

c, 1356 - 998

= 358

d, 117 + 57 - 17 

= ( 117 - 17 ) + 57 

= 100 + 57 

= 157 

Bài 5 :

a, 3^4 . 3^15 

= 3^19

b, 8^8 : 8^8 

= 1 

c, 100 - [ 120 - ( 15 - 5 )^2 ]

= 100 - ( 120 - 100 )

= 100 - 20 = 80

bai 4 : a) = 2500

b)=48

c)=157

bai 5 : a)= 1162261467

b)=1

c)= 80

a, 11 - ( 15 + 11 ) = x - ( 25 - 9 )

11-15-11=x-25+9

-15=x-16

x=1

b, 2 - x = 17 - ( - 5 )

2-x=22

x=-20

c, x - 12 = ( - 9 ) - 15

x-12=-24

x=-12

d, 9 - 25 = ( 7 - x ) - ( 25 + 7 )

(7-x)-32=-16

7-x=16

x=-9

#H

a) 15 – ( 4 – x) = 6 

=>  4 – x= 15 - 6

=>  4 – x= 9

=>  x= 4 - 9 

=>  x= -5

Easy!

a) \(15-\left(4-x\right)=6\)

\(\Leftrightarrow4-x=15-6\)

\(\Leftrightarrow4-x=9\)

\(\Leftrightarrow x=4-9\)

\(\Leftrightarrow x=-5\)

Vậy \(x=-5\)

b) \(-30+\left(25-x\right)=-1\)

\(\Leftrightarrow\left(25-x\right)=-1-\left(-30\right)\)

\(\Leftrightarrow25-x=29\)

\(\Leftrightarrow x=25-29\)

\(\Leftrightarrow x=-4\)

c) \(x-\left(12-25\right)=-8\)

\(\Leftrightarrow x-\left(-13\right)=-8\)

\(\Leftrightarrow x=-8+-13\)

\(\Leftrightarrow x=-21\)

Vậy \(x=-21\)

d) \(\left(x-29\right)-\left(17-38\right)=-9\)

\(\Leftrightarrow\left(x-29\right)-\left(-21\right)=-9\)

\(\Leftrightarrow x-29=-9+\left(-21\right)\)

\(\Leftrightarrow x-29=-30\)

\(\Leftrightarrow x=-30+29\)

\(\Leftrightarrow x=-1\)

Vậy \(x=-1\)

\(a.15-\left(4-x\right)=6\)

\(4-x=15-6\)

\(4-x=9\)

\(x=4-9\)

\(x=-5\)

Vậy \(x\in\left\{-5\right\}\)

\(b.-30+\left(25-x\right)=-1\)

\(25-x=-1-\left(-30\right)\)

\(25-x=29\)

\(x=25-29\)

\(x=-4\)

Vậy \(x\in\left\{-4\right\}\)

\(c.x-\left(12-25\right)=-8\)

\(x-\left(-13\right)=-8\)

\(x=-8+\left(-13\right)\)

\(x=-21\)

Vậy \(x\in\left\{-21\right\}\)

\(d.\left(x-29\right)-\left(17-38\right)=-9\)

\(\left(x-29\right)-\left(-21\right)=-9\)

\(x-29=-9+\left(-21\right)\)

\(x-29=-30\)

\(x=-30+29\)

\(x=-1\)

Vậy \(x\in\left\{-1\right\}\)

Bài 2:

\(a,45+170+25+30\)

\(=\left(45+25\right)+\left(170+30\right)\)

\(=60+200=260\)

Bài 3:

\(a,\left(x-6\right).5=150\)

\(x-6=150:5\)

\(x-6=30\)

\(x=30+6\)

\(x=36\)

\(b,2^5.\left(3x-2\right)=2^3.2^6\)

\(2^5.\left(3x-2\right)=2^{3+6}\)

\(2^5.\left(3x-2\right)=2^9\)

\(3x-2=2^9:2^5\)

\(3x-2=2^4=16\)

\(3x=16+2\)

\(3x=22\)

\(x=22:3\)

\(x\approx7,3\)

\(c,100-7.\left(x-5\right)=51\)

\(7.\left(x-5\right)=100-51\)

\(7.\left(x-5\right)=49\)

\(x-5=49:7\)

\(x-5=7\)

\(x=7+5\)

\(x=12\)

Phần d) bạn thiếu dữ liệu ạ.

Giúp với ạ 

Giúp với ạ 

a: =>x/15=-3/5

=>x=-9

b: =>36/y=4/7

=>y=36:4/7=63

c: =>xy=-12

=>(x,y) thuộc {(-1;12); (12;-1); (1;-12); (-12;1); (2;-6); (-6;2); (6;-2); (-2;6); (3;-4); (-4;3); (-3;4); (4;-3)}

d: =>xy=-18

=>(x,y) thuộc {(1;-18); (-18;1); (-1;18);(18;-1); (2;-9); (-9;2); (-2;9); (9;-2); (3;-6); (-6;3); (-3;6); (6;-3)}

a, 35 ⋮ (x+3) => (x+3) ∈ Ư(35) = {1;5;7;35} => x ∈ {2;4;32}

b, (x+7) ⋮ 25 và x < 100

Vì (x+7) ⋮ 25 => x+7 ∈ B(25) = {0;25;50;75;...}

Mà x < 100 => x+7 ∈ {0;25;50;75}

=> x ∈ {18;43;68}

c, (x+13) ⋮ (x+1)

Ta có: x+13 = x+1+12

Vì (x+1) ⋮ (x+1) nên để (x+13) ⋮ (x+1) thì 12 ⋮ (x+1)

=> (x+1) ∈ Ư(12) = {1;2;3;4;6;12} => x ∈ {0;1;2;3;5;11}

d, 91 ⋮ x; 26 ⋮ x và 10 < x < 30

Vì 91 ⋮ x; 26 ⋮ x => x ∈ ƯC(26;91)

Ta có: 26 = 2.13; 91 = 7.13

=> ƯCLN(26;91) = 13

=> x ∈ Ư(13) = {1;13}

Mà 10 < x < 30 => x = 13

e, (x+2) ⋮ 10, (x+2) ⋮ 15, (x+2) ⋮ 25 và x < 200

Vì (x+2) ⋮ 10, (x+2) ⋮ 15, (x+2) ⋮ 25 nên (x+2) ∈ BC(10;15;25)

Ta có: 10 = 2.5; 15 = 3.5; 20 =  2 2 . 5

=> BCNN(10;15;20) =  2 2 . 3 . 5 = 60

=> (x+2) ∈ B(60) = {0;60;120;180;...}

Mà x < 200 => x ∈ {58;118;178}

a )   x :   − 7   –  6  =   − 15  x :   − 7   =   − 9 x  =   − 9 . − 7   x  =  63

b ) x :  12  –  12  =   − 37 x :  12  =   − 25 x  =   − 25 . 12 x  = 3 00

c ) x :   − 25   +  81  =  85 x :   − 25   =  4 x  =  4 . − 25 x  = − 1 00