bài 2) a) \(2\left(x+1\right)=0\Leftrightarrow x+1=0\Leftrightarrow x=-1\) vậy \(x=-1\)

b) \(x\left(x-2\right)=0\Leftrightarrow\left\{{}\begin{matrix}x=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=0\\x=2\end{matrix}\right.\) vậy \(x=0;x=2\)

c) \(\left(x-1\right)\left(x+7\right)=0\Leftrightarrow\left\{{}\begin{matrix}x-1=0\\x+7=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\x=-7\end{matrix}\right.\) vậy \(x=1;x=-7\)

d) \(\left(x+2\right)\left(x^2-9\right)=0\Leftrightarrow\left\{{}\begin{matrix}x+2=0\\x^2-9=0\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=-2\\x^2=9\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=-2\\\left\{{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\end{matrix}\right.\) vậy \(x=-2;x=3;x=-3\)

e) \(x^2\left(x-5\right)+2\left(x-5\right)=0\Leftrightarrow\left(x^2+2\right)\left(x-5\right)=0\)

\(\Leftrightarrow\left\{{}\begin{matrix}x^2+2=0\\x-5=0\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x\in\varnothing\\x=5\end{matrix}\right.\) vậy \(x=5\)

bài 1) \(A=48+\left(-48-174\right)+\left|-74\right|=48-48-174+74=-100\)

\(B=\left(-123\right)+77+\left(-257\right)-23-43=-123+77-257-23-43=-369\)

\(C=\left(-57\right)+\left(-159\right)+47+169=-57-159+47+169=0\)

quá hợp lí

dái wa      

Giúp mình đi mình đang cần gấp

bài 2

a) 2448:[119-(x-6)]=24                          

119-(x-6)=2448:24                                

119-(x-6)=102

x-6=119-102

x-6=17

x=17+6

x=23

Câu 1:

a) Ta có: 2n+1 là số lẻ∀n

⇒\(\left(-1\right)^{2n+1}=-1\)

Ta có: \(\left(-25\right)\cdot21\cdot\left(-2\right)^2\cdot\left(-\left|-3\right|\right)\cdot\left(-1\right)^{2n+1}\)

\(=-25\cdot21\cdot4\cdot\left(-3\right)\cdot\left(-1\right)\)

\(=75\cdot84\cdot\left(-1\right)\)

\(=-6300\)

b) Ta có: \(\left(-5\right)^3\cdot67\cdot\left(-\left|-2^3\right|\right)\cdot\left(-1\right)^{2n}\)

\(=-125\cdot67\cdot\left(-8\right)\)

\(=1000\cdot67=67000\)

c) Ta có: \(35\cdot18-5\cdot7\cdot28\)

\(=35\cdot18-35\cdot28\)

\(=35\cdot\left(18-28\right)=35\cdot\left(-10\right)=-350\)

d) Ta có: \(24\cdot\left(16-5\right)-16\cdot\left(24-5\right)\)

\(=24\cdot16-24\cdot5-24\cdot16+16\cdot5\)

\(=-24\cdot5+16\cdot5\)

\(=5\cdot\left(-24+16\right)=5\cdot\left(-8\right)=-40\)

e) Ta có: \(29\cdot\left(19-13\right)-19\cdot\left(19-13\right)\)

\(=6\cdot\left(29-19\right)=6\cdot10=60\)

g)Sửa đề: \(31\cdot\left(-18\right)+31\cdot\left(-81\right)-31\)

Ta có: \(31\cdot\left(-18\right)+31\cdot\left(-81\right)-31\)

\(=31\cdot\left(-18-81-1\right)\)

\(=31\cdot\left(-100\right)=-3100\)

h) Ta có: \(\left(-12\right)\cdot47+\left(-12\right)\cdot52+\left(-12\right)\)

\(=-12\cdot\left(47+52+1\right)\)

\(=-12\cdot100=-1200\)

k) Ta có: \(13\cdot\left(23+22\right)-3\cdot\left(17+28\right)\)

\(=13\cdot45-3\cdot45\)

\(=45\cdot\left(13-3\right)=45\cdot10=450\)

m) Ta có: \(-48+48\cdot\left(-78\right)+48\cdot\left(-21\right)\)

\(=48\cdot\left(-1-78-21\right)\)

\(=48\cdot\left(-100\right)=-4800\)

n) Ta có: \(135\cdot\left(171-123\right)-171\cdot\left(135-123\right)\)

\(=135\cdot171-135\cdot123-171\cdot135+171\cdot123\)

\(=123\cdot\left(-135+171\right)=123\cdot36=4428\)

b) -26 - ( x - 7 ) = 0

               x - 7   = -26 - 0

                x - 7  = -26

                x        = -26 + 7

                 x       = -19

Bài 2 :

a) 3 - ( 17 - x ) = -12

          ( 17 - x ) = 3 - ( -12 )

          ( 17 - x ) = 15

                    x  = 17 - 15

                    x  = 2

b) -26 - ( x - 7)=0

             x - 7 = -26 -0

            x - 7 = -26

              x = -26 + 7

             x = -19

d) 135(-12 + 247) - 147(135 - 12)= -12.135 + 135.147 - 147.135 + 12.147 = (-12.135 + 12.147) + (135.147 - 147.135) = 12(-135 + 147) + 0 = -12.12 = -144

Bài 1:

a) [3.(-2) - (-8)].(-7) - (-2).(-5) = -7(-6 + 8) - 2.5= -7.2 - 2.5 = -2(7 + 5) = -2.12 = -24

c) 12 + (-47).12 - 6.(-12) = 12 - 47.12 + 6.12 = 12(1 - 47 + 6) = 12.(-40) = -480

2, 

a) \(315-\left(135-x\right)=215\)

\(\Rightarrow135-x=315-215\)

\(\Rightarrow135-x=100\)

\(\Rightarrow x=135-100\)

\(\Rightarrow x=35\)

b) \(x-320:32=25\cdot16\)

\(\Rightarrow x-10=5^2\cdot4^2\)

\(\Rightarrow x-10=20^2\)

\(\Rightarrow x-10=400\)

\(\Rightarrow x=410\)

c) \(3\cdot x-2018:2=23\)

\(=3\cdot x-1009=23\)

\(\Rightarrow3\cdot x=1032\)

\(\Rightarrow x=1032:3\)

\(\Rightarrow x=344\)

d) \(280-9\cdot x-x=80\)

\(\Rightarrow280-x\cdot\left(9+1\right)=80\)

\(\Rightarrow280-10\cdot x=80\)

\(\Rightarrow10\cdot x=280-80\)

\(\Rightarrow10\cdot x=200\)

\(\Rightarrow x=20\)

e) \(38\cdot x-12\cdot x-x\cdot16=40\)

\(\Rightarrow x\cdot\left(38-12-16\right)=40\)

\(\Rightarrow x\cdot10=40\)

\(\Rightarrow x=40:10\)

\(\Rightarrow x=4\)

bài 1 cậu ko giải giúp mình dc à

a) x - 7 = 5. 0 => x - 7 = 0 =>x = 7.

b) x: 3 = 47 +13 => x: 3 = 60 => x = 60.3 => x = 180.

c) x :  7 - 7 = 0 hoặc x : 12 - 12 = 0. Do đó x = 49 hoặc x = 144.

d) x : 2 = 150 - 135 => x: 2 = 15 => x = 15.2 => x = 30.

e) 100: x = 140 -120 => 100: x = 20 => x = 100:20 => x = 5.

g) x : 5 = 300 - 273 => x : 5 = 27 =>x = 27.5 => x = 135