a) \(6-2\left(x+4\right)=-4\)

\(\Leftrightarrow6-2x-8=-4\)

\(\Leftrightarrow-2-2x=-4\)

\(\Leftrightarrow-2x=-4+2\)

\(\Leftrightarrow-2x=-2\)

\(\Leftrightarrow x=1\)

Vậy \(x=1\)

b) tự làm.

c) \(2x-15:5=-7\)

\(\Leftrightarrow2x-7,5=-7\)

\(\Leftrightarrow2x=-7+7,5\)

\(\Leftrightarrow2x=0,5\)

\(\Leftrightarrow x=0,25\)

\(\Leftrightarrow x=\dfrac{1}{4}\)

Vậy \(x=\dfrac{1}{4}\)

d) \(231-\left(x-6\right)=1339:13\)

\(\Leftrightarrow231-x+6=103\)

\(\Leftrightarrow237-x=103\)

\(\Leftrightarrow237-x+6=103\)

\(\Leftrightarrow-x=103-237\)

\(\Leftrightarrow-x=-134\)

\(\Leftrightarrow x=134\)

e) đề j mà có 2 dấu bằng >> sai :v

f) \(28-x^3=1\)

\(\Leftrightarrow-x^3=1-28\)

\(\Leftrightarrow-x^3=-27\)

\(\Leftrightarrow x^3=27\)

\(\Leftrightarrow x^3=3^3\)

\(\Leftrightarrow x=3\)

Vậy \(x=3\)

g) \(\left(x+2\right)^3=27\)

\(\Leftrightarrow\left(x+2\right)^3=3^3\)

\(\Leftrightarrow x+2=3\)

\(\Leftrightarrow x=3-2\)

\(\Leftrightarrow x=1\)

Vậy \(x=1\)

h) \(81-\left(x-5\right)^2=56\)

\(\Leftrightarrow-\left(x-5\right)^2=56-81\)

\(\Leftrightarrow-\left(x-5\right)^2=-25\)

\(\Leftrightarrow\left(x-5\right)^2=25\)

\(\Leftrightarrow x-5=\pm5\)

\(\Leftrightarrow\left[{}\begin{matrix}x-5=5\\x-5=-5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=5+5\\x=-5+5\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=10\\x=0\end{matrix}\right.\)

Vậy \(x_1=0;x_2=10\)

j) \(x^2=9\)

\(\Leftrightarrow x=\pm3\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)

Vậy \(x_1=-3;x_2=3\)

l) tự làm.

a) \(6-2x-8=-4\Leftrightarrow2x=2\Leftrightarrow x=1\)

b) \(6⋮x\Rightarrow x=\left\{-6;-3;-2;-1;1;2;3;6\right\}\)

c) \(2x-3=-7\Leftrightarrow2x=-4\Leftrightarrow x=-2\)

d) \(231-x+6=103\Leftrightarrow x=124\)

e) hình như sai đề

f) \(x^3=27\Leftrightarrow x=3\)

g) \(x+2=3\Leftrightarrow x=1\)

h) \(\left(x+5\right)^2=25\Leftrightarrow x+5=5\Leftrightarrow x=0\)

i) \(x^2=9\Leftrightarrow\orbr{\begin{cases}x=-3\\x=3\end{cases}}\)

j) \(14⋮\left(x+3\right)\Rightarrow x=\left\{-17;-10;-5;-4;-2;4;11\right\}\)

\(7^6+7^5-7^4\)

\(=7^4\left(7^2+7-1\right)\)

\(=7^4\cdot55⋮55\)

\(16^5+2^5\)

\(=\left(2^4\right)^5+2^5\)

\(=2^{20}+2^5\)

\(=2^5\left(2^{15}+1\right)\)

\(=2^5\cdot32769⋮33\)

\(81^7-27^9-9^{13}\)

\(=\left(3^4\right)^7-\left(3^3\right)^9-\left(3^2\right)^{13}\)

\(=3^{28}-3^{27}-3^{26}\)

\(=3^{26}\left(3^2-3-1\right)\)

\(=3^{26}\cdot5\)

\(=3^{22}\cdot405⋮405\)

Ta có : (x + 3) + (x + 5) + (x + 7) + ..... + (x + 21) =  335

=> x + x + x + x + (3 + 5 + 7 + ..... + 21) = 335

=> 10x + 120 = 335

=> 10x = 335 - 120

=> 10x = 215

=> x = 21,5 

ta có : (x + 3) + (x + 5) + (x + 7) + ..... + (x + 21) =  335

<=> x + x + x + x + (3 + 5 + 7 + ..... + 21) = 335

<=> 10x + 120 = 335

=> 10x = 335 - 120

=> 10x = 215

vậy x = 21,5 

(158-x):7=20

=>185-x=20.7

=>185-x=140

=>x=185-140

=>x=45

tíc mình nha

Minh Ánh bn ơi còn mấy bài nữa mà bn giúp mk với mk sẽ hậu tạ

\(a,x\left(-3x+5\right)+3x\left(x+1\right)-40=0\)

\(\left(x.-3x\right)+\left(5x\right)+3x\left(x+1\right)-40=0\)

\(-3x^2+5x+\left(3x.x\right)+\left(3x.1\right)-40=0\)

\(-3x^2+5x+3x^2+3x-40=0\)

\(\left(-3x^2+3x^2\right)+5x+3x-40=0\)

\(8x-40=0\)

\(8x=0+40=40\)

\(x=40:8=5\)

a) \(x\left(5-3x\right)+3x\left(x+1\right)-40=0\)

\(\Rightarrow5x-3x^2+3x^2+3x-40=0\)

\(\Rightarrow8x-40=0\)

\(\Rightarrow8x=40\)

\(\Rightarrow x=5\)

b) \(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)

\(\Rightarrow48x^2-12x-20x+5+3x-48x^2-7+112x=81\)

\(\Rightarrow83x=83\)

\(\Rightarrow x=1\)

có làm thì mới có ăn nhé bạn

419 bn nha 

= 419^^

         HT

lớp 6 ai chơi được

\(231-\left(x-6\right)=1339\div13\)

\(231-\left(x-6\right)=103\)

\(x-6=231-103\)

\(x-6=128\)

\(x=128+6\)

\(x=134\)

     231-(x-6)=1339:13

=> 231-(x-6)=103

=> x-6=231-103

=> x-6=128

=> x=128+6

=> x=134

231-(x-6)=1339:13

\(\Rightarrow\)231-(x-6)=103

\(\Rightarrow\)x-6=231-103

\(\Rightarrow\)x-6=128

\(\Rightarrow\)x=128+6

\(\Rightarrow\)x=134.