a) (5x³ – 2x² + 4x – 4) . ( x³ + 3x² – 5)

= 5x³ . ( x³ + 3x² – 5) - 2x² . ( x³ + 3x² – 5) + 4x . ( x³ + 3x² – 5) – 4 . ( x³ + 3x² – 5)

= 5x³ . x³ + 5x³ . 3x² + 5x³ . (-5) – [ 2x² . x³ + 2x² . 3x² +2x² . (-5)] + [4x . x³ + 4x. 3x² + 4x . (-5)] – [ 4x³ + 4.3x² + 4.(-5)]

= 5x⁶ + 15x⁵ – 25x³ – (2x⁵ + 6x⁴ – 10x²) + 4x⁴ + 12x³ – 20x – (4x³ + 12x² – 20)

= 5x⁶ + 15x⁵ – 25x³ – 2x⁵ - 6x⁴ + 10x² + 4x⁴ + 12x³ – 20x – 4x³ - 12x² + 20

= 5x⁶ + (15x⁵ – 2x⁵ ) + (- 6x⁴ + 4x⁴ ) + (-25x³ + 12x³ – 4x³ ) + (10x² - 12x² ) – 20x + 20

= 5x⁶ + 13x⁵ – 2x⁴ – 17x³ -2x² – 20x + 20

b) (-2,5.x⁴ + 0,5x² + 1) . (4x³ – 2x + 6)

= -2,5.x⁴ . (4x³ – 2x + 6) + 0,5x² . (4x³ – 2x + 6) + 1. (4x³ – 2x + 6)

= (-2,5.x⁴) . 4x³ + (-2,5.x⁴ ) . (-2x) + (-2,5.x⁴ ) . 6 + 0,5x² . 4x³ + 0,5x² . (-2x) + 0,5x² . 6 + 4x³ – 2x + 6

= -10x⁷ + 5x⁵ – 15x⁴ + 2x⁵ – x³ + 3x² + 4x³ – 2x + 6

= -10x⁷ + ( 5x⁵ + 2x⁵ ) - 15x⁴ + (– x³ + 4x³ ) + 3x² – 2x + 6

= -10x⁷ +7x⁵ - 15x⁴ + 3x³ + 3x² – 2x + 6

1) \(|5x-3|=|7-x|\)

\(\Leftrightarrow\orbr{\begin{cases}5x-3=7-x\\5x-3=x-7\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}6x=10\\4x=-4\end{cases}}\)

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

Vậy...

2) \(2.|3x-1|-3x=7\)

\(\Leftrightarrow2.|3x-1|=7+3x\)

\(\Leftrightarrow\orbr{\begin{cases}2.\left(3x-1\right)=7+3x\\2.\left(3x-1\right)=-7-3x\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}6x-2=7+3x\\6x-2=-7-3x\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}3x=9\\9x=-5\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=3\\x=\frac{-5}{9}\end{cases}}\)

Vậy...

5) \(\text{1,6 - |x + 1,5| = 0}\)

\(|x + 1,5| = 1,6-0\)

\(\text{|x + 1,5| = 1,6}\)

\( |x | = 1,6-1,5\)

\(|x|=0,1\)

mình cần khá gấp nhe

\(\left(5x-1\right)\left(\frac{2x-1}{3}\right)=0\)

\(\Leftrightarrow\left(\frac{\left(5x-1\right)\left(2x-1\right)}{3}\right)=0\)

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

\(\Rightarrow\orbr{\begin{cases}5x-1=0\\2x-1=0\end{cases}}\)\(\Rightarrow\orbr{\begin{cases}x=\frac{1}{5}\\x=\frac{1}{2}\end{cases}}\)

Vậy \(x=\frac{1}{5}\)hoặc\(x=\frac{1}{2}\)

b) \(\left(-0,6x-\frac{1}{2}\right).\frac{3}{4}-\left(-1\right)=\frac{1}{3}\)

\(\Leftrightarrow\left(-0,6x-\frac{1}{2}\right).\frac{3}{4}=\frac{-2}{3}\)

\(\Leftrightarrow\left(-0,6x-\frac{1}{2}\right)=\frac{-8}{9}\)

\(\Leftrightarrow-0,6x=\frac{-7}{18}\)

\(\Rightarrow x=\frac{35}{54}\)

_Thần đồng ngu học (Toàn bài dễ)

a) x/7 = 6/21

x/7 = 2/7

=>x=2

b)2/3x -1/2=1/10

2/3x = 1/10+1/2

2/3x = 3/5

x=3/5:2/3

x=9/10

c)1/4+1/3 : x = -5

d)3x+17=2

đ)2/3x +1/4 =7/12

2x+3/10= 11/6 . 6/11

x : 4 1/3 = -2,5

a) x/7 = 6/21

x/7 = 2/7

=>x=2

b)2/3x -1/2=1/10

2/3x = 1/10+1/2

2/3x = 3/5

x=3/5:2/3

x=9/10

c)1/4+1/3 : x = -5

d)3x+17=2

đ)2/3x +1/4 =7/12

2x+3/10= 11/6 . 6/11

x : 4 1/3 = -2,5

a: \(\Leftrightarrow\left(x-\dfrac{2}{5}\right):\dfrac{3}{2}=-\dfrac{5}{4}+\dfrac{5}{2}=\dfrac{5}{4}\)

\(\Leftrightarrow x-\dfrac{2}{5}=\dfrac{5}{4}\cdot\dfrac{3}{2}=\dfrac{15}{8}\)

hay x=91/40

b: \(\Leftrightarrow\left(2.5x-3.6\right)=-1\cdot\dfrac{12}{7}=\dfrac{-12}{7}\)

=>2,5x=66/35

hay x=132/175

c: \(\Leftrightarrow\left(\dfrac{15}{4}-2x\right)=\dfrac{19}{9}:\dfrac{4}{3}=\dfrac{19}{9}\cdot\dfrac{3}{4}=\dfrac{19}{12}\)

=>2x=15/4-19/12=45/12-19/12=26/12

=>x=13/12

a: =>2x=5/4+4/15=91/60

=>x=91/120

b: =>2,5-x=-5/2*1/4=-5/8=-0,625

=>x=3,125

a, 2x + 27 = -11

=> 2x = -11 - 27

=> 2x = -38

=> x = -38 : 2

=> x = -19

vậy___

b, 3x + 26 = 6

=> 3x = 6 - 26

=> 3x = -20

=> x = -20/3

vậy___

c, \(x\div4\frac{1}{2}=2,5\)

\(\Rightarrow x\div4,5=2,5\)

\(\Rightarrow x=4,5\cdot2,5\)

\(\Rightarrow x=11,25\)

vậy___

\(\frac{3}{4x}=\frac{1}{2}\)    đk: x khác 0

\(\Rightarrow\frac{3}{4x}=\frac{3}{6}\)

=> 4x = 6

=> x = 4/6 = 2/3

vậy___

a)  2x + 27 = -11

      2x  =  -11  - 27 =-28

=>   \(x=-\frac{28}{2}=-14\)

B)  3x + 26 = 6

     3x   = 6 - 26  = -20

     \(x=-\frac{20}{3}\)

C)  ko rõ đề

D)  \(\frac{3}{4x}=\frac{1}{2}\)

  \(3\cdot2=4x\)

   6= 4x  

=>  x  = \(\frac{6}{4}=\frac{3}{2}\)

hok tốt .

a) 2x + 27 = -11

=> 2x        = -11 - 27

=> 2x        = -38

=> x          = -38 : 2

=> x          = -19

b) 3x + 26 = 6

=> 3x        = 6 - 26

=> 3x        = -20

=> x          = \(\frac{-20}{3}\)

c) x : \(4\frac{1}{2}\)= 2,5

=> x : \(\frac{9}{2}\)= \(\frac{5}{2}\)

=> x             = \(\frac{5}{2}.\frac{9}{2}\)

=> x             = \(\frac{45}{4}\)

d) \(\frac{3}{4}x=\frac{1}{2}\)

=> x = \(\frac{1}{2}:\frac{3}{4}\)

=> x = \(\frac{1}{2}.\frac{4}{3}\)

=> x = \(\frac{2}{3}\)

Giữ lời hứa nka Nguyễn Mạnh Tân!

làm nhanh mình k cho

Hứa k r lm cko! Bài dài lắm

( 0,25x ) : 3 = 5/6 : 0,125

( 1/4x ) : 3 = 5/6 : 1/8

( 1/4x ) : 3 = 5/6 x 8

( 1/4x ) : 3 = 20/3

1/4x          = 20/3 x 3

1/4x         = 20

x              = 20 : 1/4

x              = 80

0,01 : 2,5 = ( 0,75x ) : 0,75

1/100 : 25/10 = (3/4x) : 3/4

1/100 x 10/25 = (3/4x) : 3/4

=>(3/4x) : 3/4 = 1/250

3/4x                = 1/250 x 3/4

3/4x                = 3/1000

x                     = 3/1000 : 3/4

x                     = 1/250

 4/3 : 0,8 = 2/3 : ( 0,1x )

<=>2/3 : (0,1x) = 4/3 : 0,8

2/3 : (0,1x) = 4/3 : 4/5

2/3 : (0,1x) = 4/3 x 5/4

2/3 : (0,1x) = 5/3

2/3 : (1/10x) = 5/3

1/10x           = 2/3 : 5/3

1/10x           = 2/3 x 3/5

1/10x           = 2/5

x                  = 2/5 : 1/10

x                  = 2/5 x 10

x                  = 4