c) (x + 9 - 17) - 24 = 11 - (x + 7)

(x + 8) - 24 = 11 - (x + 7)

(x + 8) - 24 = 11 - x - 7

x-8-24=11-x-7

x-8-24=4-x

x -32 = 4 -x 

x + x -32 =4

x + x = 4 +32

2x=36

x=18

a) -5x - 2⁵ = 3x + 2³

    -5x - 32 = 3x + 8

   -5x - 3x - 32 = 8

  -5x - 3x = 8 +32

  -8x = 8+32

  -8x = 40

   x= -5

a \(\dfrac{6}{15}+\dfrac{11}{15}=\dfrac{17}{15}\)

b \(\dfrac{22}{77}-\dfrac{14}{77}=\dfrac{8}{77}\)

c \(\dfrac{11}{13}\times\dfrac{26}{31}=11\times\dfrac{2}{31}=\dfrac{22}{31}\)

d \(\dfrac{1}{2}\times3\times\dfrac{2}{5}=\dfrac{3}{5}\)

mình cảm ơn

a, ( x + 1 ) + ( x + 2 ) + ... + ( x + 199 ) = 0

x + 1 + x + 2 + ... + x + 199 = 0

( x + x + ... + x ) + ( 1 + 2 + ... + 199 ) = 0 

199x + 19900 = 0

199x = 0 - 19900

199x = -19900

x = -19900 : 199

x = -100

Vậy ...

b, ( x - 30 ) + ( x - 29 ) + ( x - 28 ) = 11

x - 30 + x - 29 + x - 28 = 11

( x + x + x ) - ( 30 + 29 + 28 ) = 11

3x -  87 = 11

3x = 11 + 87 

3x = 98

x = \(\frac{98}{3}\)

Vậy ... 

`@` `\text {Ans}`

`\downarrow`

\(39 \times 123 + 26 \times 47 - 13 \times 163\)

`= 3 \times 13 \times 123 + 2 \times 13 \times 47 - 13 \times 163`

`= 13 \times (3 \times 123 + 2 \times 47 - 163)`

`= 13 \times (369 + 94 - 163)`

`= 13 \times 300`

`=3900`

\(39\times123+26\times47-13\times163\)

\(=13\times\left(3\times123+2\times47-163\right)\)

\(=13\times300\)

\(=3900\)

a, \(B=\dfrac{1}{13}\left(\dfrac{-65}{x-7}+\dfrac{26}{x-7}\right)\)

\(=\dfrac{1}{13}\left(\dfrac{-65+26}{x-7}\right)=\dfrac{1}{13}.\dfrac{-39}{x-7}=\dfrac{-3}{x-7}=-\dfrac{3}{x-7}\)

b, Để B đạt giá trị nguyên thì \(\dfrac{3}{x-7}\) phải đạt giá trị nguyên.

\(\Rightarrow x-7\inƯ\left(3\right)\Rightarrow x-7\in\left\{-3;-1;1;3\right\}\)

\(\Rightarrow x\in\left\{4;6;8;10\right\}\)

Vậy...........

Chúc bạn học tốt!!!

\(B=\dfrac{1}{13}\left(\dfrac{-65}{x-7}+\dfrac{26}{x-7}\right)\)

\(B=\dfrac{-65}{13\left(x-7\right)}+\dfrac{26}{13\left(x-7\right)}\)

\(B=\dfrac{-65}{13x-91}+\dfrac{26}{13x-91}\)

\(B=\dfrac{-39}{13x-91}\)

\(B\in Z\Rightarrow\left\{{}\begin{matrix}-65⋮x-7\\26⋮x-7\end{matrix}\right.\)

\(\Rightarrow x-7\in UC\left(-65;26\right)\)

\(UCLN\left(-65;26\right)=13\)

\(\Rightarrow\left[{}\begin{matrix}x-7=13\Rightarrow x=20\\x-7=-13\Rightarrow x=-6\\x-7=1\Rightarrow x=8\\x-7=-1\Rightarrow x=6\end{matrix}\right.\)

Tính giá trị của biểu thức sau:

a) (-7)+(-14) = -21

b) (-35)+(-9) = -44

c) (-5)+(-248) = -253

d) (-23)+105 = +(105-23) = 82

e) 78+(-123) = -(123-78) = 45

f) 23+(-13) = +(23-13) = 10

g) (-23)+13 = -(23-13) = -10

i) 26+(-6) = +(26-6)= 20.

b) \(\frac{26+x}{39-x}=\frac{6}{7}\)

=> 7( 26+ x) = 6(39-x) 

=>182 +7x  = 234 - 6x

=> 7x+6x = 234-182

=> 13x= 52 

=> x=4

a) \(\frac{26+x}{39+x}=\frac{6}{7}\)

=> 7(26+x) = 6(39+x) 

=> 182 + 7 x = 234 + 6x 

=> 7x - 6x = 234 - 182 

=> x = 52 

a,\(B=\dfrac{1}{13}\left(\dfrac{-65}{x-7}+\dfrac{26}{x-7}\right)\)

\(B=\dfrac{1}{13}\left(\dfrac{-65+26}{x-7}\right)\)

\(B=\dfrac{1}{13}\left(\dfrac{-39}{x-7}\right)\)