Giải các phương trình sau:
1. a) 7x+12=0. b) 12-6x=0. c) 12-6x=0. d)-2x+14=0
2. a) 3x +1=7x-11. b)2x+x+12=0. c). x-5=3-x. d) 7-3x=9-x
e)5-3x=6x+7. f)11-2x=x-1. g)15-8x=9-5x. h)3+2x=5+2x
Giải các phương trình sau:
1. a) 7x+12=0. b) 12-6x=0. c) 12-6x=0. d)-2x+14=0
2. a) 3x +1=7x-11. b)2x+x+12=0. c). x-5=3-x. d) 7-3x=9-x
e)5-3x=6x+7. f)11-2x=x-1. g)15-8x=9-5x. h)3+2x=5+2x
1. a. 7x + 12 = 0
$\Leftrightarrow$ 7x = -12
$\Leftrightarrow$ x = $\frac{-12}{7}$
S = { $\frac{-12}{7}$ }
b. 12 – 6x = 0
$\Leftrightarrow$ 6( 2 – x ) = 0
$\Leftrightarrow$ 2 – x = 0
$\Leftrightarrow$ x = 2
S = { 2 }
c. 12 – 6x = 0
$\Leftrightarrow$ 6( 2 – x ) = 0
$\Leftrightarrow$ 2 – x = 0
$\Leftrightarrow$ x = 2
S = { 2 }
d. -2x + 14 = 0
$\Leftrightarrow$ -2( x – 7) = 0
$\Leftrightarrow$ x – 7 = 0
$\Leftrightarrow$ x = 7
Bài 2:
a. 3x + 1 = 7x – 11
$\Leftrightarrow$ 3x – 7x = -11 -1
$\Leftrightarrow$ -4x = -12
$\Leftrightarrow$ x = 3
b. 2x + x + 12 = 0
$\Leftrightarrow$ 3x = -12
$\Leftrightarrow$ x = -4
c. x – 5 = 3 – x
$\Leftrightarrow$ x + x = 3 + 5
$\Leftrightarrow$ 2x = 8
$\Leftrightarrow$ x = 4
d. 7 – 3x = 9 – x
$\Leftrightarrow$ -3x + x = 9 – 7
$\Leftrightarrow$ -2x = 2
$\Leftrightarrow$ x = -1
e. 5 – 3x = 6x + 7
$\Leftrightarrow$ -3x – 6x = 7 – 5
$\Leftrightarrow$ -9x = 2
$\Leftrightarrow$ x=$\frac{-2}{9}$
f. 11 – 2x = x – 1
$\Leftrightarrow$ -2x -x = -1 – 11
$\Leftrightarrow$ -3x = -12
$\Leftrightarrow$ x = 4
g. 15 – 8x = 9 – 5x
$\Leftrightarrow$ -8x + 5x = 9 – 15
$\Leftrightarrow$ 3x = -6
$\Leftrightarrow$ x = -2
h. 3 + 2x = 5 + 2x
$\Leftrightarrow$ 2x – 2x = 5 – 3
$\Leftrightarrow$ 0 = 2 ( vô lí )
1.
a) 7x+12=0
⇔7x= -12
⇔x=-12/7
b) 12-6x=0
⇔6x=12
⇔x=2
c) giống b
d)-2x+14=0
⇔-2x=-14
⇔x=7
2.
a) 3x +1=7x-11
⇔-4x=-12
⇔x=3
b)2x+x+12=0
⇔3x+12=0
⇔3x= -12
⇔x= -4
c).x-5=3-x.
⇔2x=8
⇔x=4
d) 7-3x=9-x
⇔-2x=2
⇔x=-1
e)5-3x=6x+7
⇔-9x=2
⇔x= -2/9
f)11-2x=x-1
⇔-3x= -12
⇔x= 4
g)15-8x=9-5x
⇔ -3x= -6
⇔x=2
h)3+2x=5+2x
⇔0x=2
⇔ pt vô nghiệm