a) 

( x + 9 ) − 25 = 23 x = 39

b) 

140 : ( x − 8 ) = 7 4 : 7 3 x − 8 = 140 : 7 x = 28

c)

100. ( x − 51 ) = 400 x = 55

55 nha bạn

\(\frac{1}{5.8}+\frac{1}{8.11}+\frac{1}{11.14}+...+\frac{1}{x\left(x+3\right)}=\frac{1}{18}\)

\(\Leftrightarrow\frac{1}{3}.\left(\frac{3}{5.8}+\frac{3}{8.11}+\frac{3}{11.14}+.....+\frac{3}{x\left(x+3\right)}\right)=\frac{1}{18}\)

\(\Leftrightarrow\frac{1}{3}.\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+....+\frac{1}{x}-\frac{1}{x+3}\right)=\frac{1}{18}\)

\(\Leftrightarrow\frac{1}{3}.\left(\frac{1}{5}-\frac{1}{x+3}\right)=\frac{1}{18}\Leftrightarrow\frac{1}{5}-\frac{1}{x+3}=\frac{1}{18}:\frac{1}{3}=\frac{1}{6}\)

\(\Leftrightarrow\frac{1}{x+3}=\frac{1}{5}-\frac{1}{6}=\frac{1}{30}\)

<=>x+3=30

<=>x=27

Vậy x=27

a) x – 32 : 16 = 48 ó x – 2 = 48 ó x = 48 + 2 ó x = 50

b) 88 – 3.(7+x) = 64 ó 3.(7+x) = 88 – 64 ó 7 + x = 24:3 ó x = 8 – 7 ó x = 1

c) (5+4x) : 3 – 121 : 11 = 4 ó (5+4x) : 3 – 11 = 4 ó (5+4x) : 3 = 4 + 11 ó 5+4x = 15.3 ó 4x = 45 – 5 ó 4x = 40 ó x = 10

d) 15 – 2(3x+1) = 11.13 – 130 ó 15 – 2(3x+1) = 143 – 130 ó 15 – 2(3x+1) = 13

ó 2(3x+1) = 15 – 13 ó 3x + 1 = 2:2 ó 3x = 1 – 1 ó 3x = 0 ó x = 0

a) \(\frac{x}{8}< \frac{1}{4}=>\frac{x}{8}-\frac{1}{4}< 0=>\frac{x}{8}-\frac{2}{8}< 0\)

\(=>\frac{x-2}{8}< 0=>\orbr{\begin{cases}x-2< 0\\8>0\end{cases}}=>\orbr{\begin{cases}x< 2\\8>0\end{cases}}\)

vay \(x< 2\)

cac cau con lai lam tuong tu

Bài 9: 

a) 15x + 40 = 15 + 20.8

    15x + 40 = 15 + 160

    15x + 40 = 175

             15x = 175 - 40 = 135

                 x = 135 / 15 = 9

b) ( x-1 )( 5-x ) = 0

  => x-1 = 0 hoặc 5-x = 0 

+) x-1 = 0         +) 5-x = 0 ( còn lại tự làm nhé ^^ )

c) x - 140 : 35 = 270

          x - 140 = 270 . 35 = 9450

                 x = 9450 + 140 = 9590

d) ( 14 - 3x ) + ( 6 + x ) = 0

    14 - 3x + 6 + x = 0

    ( 14 + 6 ) - ( 3x -x ) = 0

                  20 - 2x = 0

                         2x = 20

                           x = 10

giúp tui với 

tui đang cần lắm đó bà con ơi

em mới lớp 5 seo anh gọi em là: BÀ CON

Ngáo hết 

Help me please

Tham khảo: