9,5 - x = 2,7

x = 9,5 - 2,7

x = 6,8

31

1. Tìm x, biết:

a) \(\frac{4}{x}=\frac{8}{6}\). Ta có: \(\frac{8}{6}=\frac{8:2}{6:2}=\frac{4}{3}\Rightarrow x=3\)

b) \(\frac{3}{x-5}=\frac{4}{x+2}\). Ta có: \(5-2=3\)

\(\Rightarrow x=\left(3.5\right)+\left(4.2\right)+3=15+8+3=26\)

c) \(\frac{x}{-2}=\frac{-8}{x}\Rightarrow x=\left(-8\right):\left(-2\right)=4\)

2. Rút gọn

a) \(\frac{2^4.5^2.11^2.7}{2^3.5^3.7^2.11}\Leftrightarrow\frac{2^3.2^1.5^2.11.11.7}{2^3.5^2.5^1.7.7.11}\Leftrightarrow\frac{2^1.11}{5^1.7}=\frac{22}{35}\)

b) Tương tự

c) Tương tự

\(\frac{4}{x}=\frac{8}{6}\Rightarrow x=\frac{4.6}{8}=3\)

\(\frac{3}{x-5}=\frac{-4}{x+2}\Rightarrow3\left(x+2\right)=-4\left(x-5\right)\)

                                \(\Rightarrow3x+6=-4x+20\)

                                \(\Rightarrow3x+4x=20-6\)

                                \(\Rightarrow7x=14\)

                                \(\Rightarrow x=2\)

\(\frac{x}{-2}=\frac{-8}{x}\Rightarrow x^2=\left(-8\right)\left(-2\right)=16\Rightarrow x=\pm4\)

\(\frac{4}{x}=\frac{8}{6}\)

\(\Rightarrow4\cdot6=x\cdot8\)

\(\Rightarrow x=\frac{4\cdot6}{8}\)

\(\Rightarrow x=3\)

\(9,5\times3,7+9,5\times1,3+9,5:0,25+9,5\)

\(=9,5\times3,7+9,5\times1,3+9,5\times4+9,5\)

\(=9,5\times\left(3,7+1,3+4+1\right)\)

\(=9,5\times10\)

\(=95\)

   \(2,5\) x \(9,5\) x \(4+20\) x \(9,5\) x \(0,5\) +\(9,5\) x \(8\) x \(1,25\)

\(=9,5\) x ( \(2,5\) x \(4+20\) x \(0,5\) + \(8\) x \(1,25\) )

\(=9,5\) x \(30\)

\(=285\)

=9.5*10+9.5*10+9.5+10

=9.5*(10+10+10)

=9.5*30

=2850

`2,5xx9,5xx4+20xx9,5xx0,5+9,5xx8xx1,25`

`=9,5xx10+9,5xx10+9,5xx10`

`=9,5xx(10+10+10)`

`=9,5xx30`

`=285`

= 9,5 x (2,5 + 4+20+0,5+8+1,25)

=9,5x36,25

=344,375

285

2,5 x 2,7 < X x 2 < 2,7 x 4,5 

6,75 < X x 2 < 12,15 

=> x = 4 ; 5 , 6 

<=>6.75<Xx2<12.15

=>X=4;5;6

2,3 x 2,7 < X x 2 < 2,7 x 4,5

6,75 < X x 2 < 12,15

=> x = 4 ; 5 ; 6

Ta có: 5².7³.11².x - 5².7².11⁴ = 0

=> 5².7².11²(7x - 11²) = 0

=> 7x - 121 = 0

=> 7x = 121

=> x = 121 : 7

=> x = 121/7