Question

Giải các PT sau:
a) 2x + 3 = -5
b) 3(x-5) + 7 = 0
c) 5 - (x+2) = 3(x-1)

Answer 1

a)    2x + 3 = -5
<=> 2x       = -5 - 3 
<=> 2x       = -8
<=>   x       = \(\dfrac{-8}{2}\)
<=>   x       = -4
Vậy S = \(\left\{-4\right\}\)

b)    3(x-5) + 7 = 0
<=> 3(x-5)       = -7
<=>   x-5         = \(\dfrac{-7}{3}\)
<=>   x            = \(\dfrac{-7}{3}\) + 5
<=>   x            = \(\dfrac{8}{3}\)
Vậy S = \(\left\{\dfrac{8}{3}\right\}\)

c) 5 - (x+2) = 3(x-1)
<=> 5 - x - 2 = 3x - 3
<=>    - x - 3x = -3 + 2 -5
<=>    -4x      = -6
<=>       x       = \(\dfrac{-6}{-4}\)
<=>       x       = \(\dfrac{3}{2}\)
 Vậy S = \(\left\{\dfrac{3}{2}\right\}\)

Answer 2

`2x + 3 = -5`

`2x = -5 - 3`

`2x = -8`

`x = -4`

Vậy `S = { -4}`

__________________

`3(x-5) + 7 = 0`

`3(x-5) = -7`

`x-5 = (-7)/3`

`x = (-7)/3 + 5`

`x= 8/3`

Vậy `S = { 8/3}`

___________________

`5-(x+2)=3.(x-1)`

`5 -x - 2 = 3x - 3`

` - x - 3x = -3 + 2 -5`

`-4x = -3 + 2 -5`

`-4x = -6`

`x = -6 : (-4)`

`x=3/2`

Vậy `S = { 3/2}`

 

Answer 3

\(a)2x+3=-5\)

\(\Leftrightarrow2x=-5-3\)

\(\Leftrightarrow2x=-8\)

\(\Leftrightarrow x=-8:2\)

\(\Leftrightarrow x=-4\)

\(b)3\left(x-5\right)+7=0\)

\(\Leftrightarrow3x-15+7=0\)

\(\Leftrightarrow3x-8=0\)

\(\Leftrightarrow3x=0+8\)

\(\Leftrightarrow3x=8\)

\(\Leftrightarrow x=8:3\)

\(\Leftrightarrow x=\dfrac{8}{3}\)

\(c)5-\left(x+2\right)=3\left(x-1\right)\)

\(\Leftrightarrow5-x-2=3\left(x-1\right)\)

\(\Leftrightarrow5-x-2=3x-3\)

\(\Leftrightarrow3-x=3x-3\)

\(\Leftrightarrow3-x-3x=-3\)

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

\(\Leftrightarrow-4x=-3-3\)

\(\Leftrightarrow-4x=-6\)

\(\Leftrightarrow-6:-4\)

\(\Leftrightarrow\dfrac{-6}{-4}=\dfrac{3}{2}\)

Answer 4

   2x + 3 = -5
=>  2x       = -5 - 3 
=> 2x       = -8
=>   x       = −82−82
=>   x       = -4
  X = -4