a) x + 15 = 36 - 2x

x + 15 = 36 - (x + x )

15 =36 - ( x + x) - x

15 = 36 - x - x - x

15 = 36 - 3x

3x = 36 - 15

3x = 21

x = 21 : 3

=> x = 7

b) (x - 7) - (2x +5) = -14

x - 7 -( 2x + 5) = -14

x - (2x + 5) = -14 + 7 = -7

x - 2x - 5 = -7

x - 2x = -7 + 5 = -2

x - x + x = 2

x = 2 (-x + x cũng bằng chính nó)

=> x = 2

c) (x - 12) - 15 = (-7 + 20) - (18+x)

(x - 12) - 15 = 13 - (18 + x)

(x - 12) - 15 = 13 - 18 - x

(x - 12) - 15 = -5 - x

15 = (x - 12 ) - (-5 - x)

15 = x - 12 + 5 + x

15 = x + (-12) + 5 + x

15 = 2x + [(-12) + 5]

15 = 2x + -7

2x = -7 + 15

2x = 8

x = 8 : 2

=> x = 4

..................

giải đi mik k cho

\(\left|x-2\right|-\frac{1}{2}=\frac{5}{2}\)

\(\Leftrightarrow\left|x-2\right|=\frac{5}{2}+\frac{1}{2}\)

\(\Leftrightarrow\left|x-2\right|=\frac{6}{2}=3\)

\(\Leftrightarrow\orbr{\begin{cases}x-2=-3\\x-2=3\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-1\\x=5\end{cases}}\)

Vậy \(x=-1\)hoặc \(x=5\)

a) 187 - {[497 - ( 8 x X + 11) : X] : 3 - 78} = 150

=> {[497 - ( 8 x X + 11) : X] : 3 - 78} = 187 - 150

=> {[497 - (8 x X + 11) : X] : 3 - 78} = 37

=> [497 - (8 x X +11): X ] : 3 - 78 = 37

=> [497 - (8 x X + 11) : X] : 3 = 115

=> 497 - ( 8 x X + 11) : X = 345

=> (8 x X  + 11) : X = 497 - 345 = 152

=> 8X + 11 = 152X

=> 152X - 8X = 11

=> 144X = 11

=> X = 11/144

b) 19,96 + 4,19 - 24,15 : \(\left(x:\frac{1}{4}-\frac{1}{4}\right)=23,15\)

=> 19,96 + 4,19 - 24,15 : \(\left(x\cdot4-\frac{1}{4}\right)=23,15\)

=> 24,15 - 24,15 : \(\left(x\cdot4-\frac{1}{4}\right)\)= 23,15

=> 24,15 : \(\left(x\cdot4-\frac{1}{4}\right)\)= 1

=> \(x\cdot4-\frac{1}{4}=24,15\)

=> \(x\cdot4=24,15+\frac{1}{4}=24,4\)

=> x = 24,4 : 4 = 6,1

Còn câu c tương tự

Lời giải:

$2\frac{2}{6}x+8\frac{2}{3}=3\frac{1}{3}$

$\frac{7}{3}x=3\frac{1}{3}-8\frac{2}{3}=\frac{-16}{3}$

$x=\frac{-16}{3}: \frac{7}{3}=\frac{-16}{7}$

----------------------

$3\frac{2}{7}x-\frac{1}{8}=2\frac{3}{4}$

$\frac{23}{7}x=2\frac{3}{4}+\frac{1}{8}$

$\frac{23}{7}x=\frac{23}{8}$

$x=\frac{23}{8}: \frac{23}{7}=\frac{7}{8}$

nè nè! Ở đây chỉ viết câu trả lời thôi à nghen

ngậm mồm

a) \(\dfrac{x}{2}+\dfrac{y}{3}=\dfrac{x+y}{2+3}\)

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

\(\dfrac{x}{2}=\dfrac{x+y}{5}-\dfrac{y}{3}\)

\(\dfrac{x}{2}=\dfrac{3\left(x+y\right)}{15}-\dfrac{5y}{15}\)

\(\dfrac{x}{2}=\dfrac{3x-2y}{15}\)

\(\Rightarrow15x=2\left(3x-2y\right)\)

\(15x=6x-4y\)

\(15x-6x=4y\)

\(9x=4y\)

(CÒN LẠI MÌNH KHÔNG BIẾT LÀM)

b) \(\dfrac{x}{3}-\dfrac{4}{y}=\dfrac{1}{5}\)

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

\(\dfrac{x}{3}=\dfrac{1}{5}+\dfrac{20}{5y}\)

\(\dfrac{x}{3}=\dfrac{1+4}{y+1}\)

\(\Rightarrow x\left(y+1\right)=15\)

(CÒN NHIÊU TỰ LÀM NHÉ)

a ) \(5\left(x^2\right)+7x+2\)

\(\Leftrightarrow5x^2+7x+2=0\)

\(\Leftrightarrow5x^2+5x+2x+2=0\)

\(\Leftrightarrow\left(5x+2\right)\left(x+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{2}{5}\\x=-1\end{matrix}\right.\)

Vậy .............

b ) \(\dfrac{x+1}{17}+\dfrac{x+2}{16}=\dfrac{x+3}{15}+\dfrac{x+4}{14}\)

\(\Leftrightarrow\dfrac{x+1}{17}+1+\dfrac{x+2}{16}+1=\dfrac{x+3}{15}+1+\dfrac{x+4}{14}+1\)

\(\Leftrightarrow\dfrac{x+18}{17}+\dfrac{x+18}{16}=\dfrac{x+18}{15}+\dfrac{x+18}{14}\)

\(\Leftrightarrow\dfrac{x+18}{17}+\dfrac{x+18}{16}-\dfrac{x+18}{15}-\dfrac{x+18}{14}=0\)

\(\Leftrightarrow\left(x+18\right)\left(\dfrac{1}{17}+\dfrac{1}{16}-\dfrac{1}{15}-\dfrac{1}{14}\right)=0\)

Vì \(\left(\dfrac{1}{17}+\dfrac{1}{16}-\dfrac{1}{15}-\dfrac{1}{14}\right)\ne0\)

Ta có : \(x+18=0\Leftrightarrow x=-18\)

Vậy ......

c ) \(\dfrac{x-1}{x-3}=\dfrac{x-4}{x-7}\)

\(\Leftrightarrow\left(x-1\right)\left(x-7\right)=\left(x-3\right)\left(x-4\right)\)

\(\Leftrightarrow x^2-7x-x+7=x^2-4x-3x+12\)

\(\Leftrightarrow-x=5\)

\(\Leftrightarrow x=-5\)

Vậy ..

cảm ơn nhiều nha