2010.2009=.........

........-2009.2009=..........

vay x=..........

\(\frac{2}{5}\cdot\frac{1}{2}-\frac{2}{5}\cdot\frac{1}{3}-\frac{2}{5}\cdot\frac{1}{6}\)

\(=\frac{2}{5}\cdot\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\)

\(=\frac{2}{5}\cdot\frac{0}{6}=\frac{2}{5}\cdot0=0\)

tìm x

a)  \(0,5+\left(x-\frac{15}{2}\right):\frac{1}{2}=\frac{9}{2}\)

\(\Rightarrow x=\frac{19}{2}=8,5\)

b) \(2012\cdot x-2010\cdot x=2014\)

  \(\Leftrightarrow\left(2012-1010\right)\cdot x=2014\)

\(\Leftrightarrow2x=2014\)

\(\Rightarrow x=\frac{2014}{2}=1007\)

hok tốt .

Tính nhanh:

2/5 x 1/2 - 2/5 x 1/3 - 2/5 x 1/6

= 2/5 x ( 1/2 - 1/3 - 1/6 )

= 2/5 x ( 3/6 - 2/6 - 1/6 )

= 2/5 x 0/6

=0

Tính nhanh :

\(\frac{2}{5}\cdot\frac{1}{2}-\frac{2}{5}\cdot\frac{1}{3}-\frac{2}{5}\cdot\frac{1}{6}\)

= \(\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\cdot\frac{2}{5}\)

= \(\left(\frac{3}{6}-\frac{2}{6}-\frac{1}{6}\right)\cdot\frac{2}{5}\)

= \(0\cdot\frac{2}{5}\)

= \(0\)

Tìm x biết :

a) a, 0,5 + ( x - \(\frac{15}{2}\) ) : \(\frac{1}{2}\)= \(\frac{9}{2}\)

         ( x - \(\frac{15}{2}\)) : \(\frac{1}{2}\)= \(\frac{9}{2}\)-   0,5

          ( x - \(\frac{15}{2}\)) : \(\frac{1}{2}\)= 4

          ( x - \(\frac{15}{2}\)) = 4 x \(\frac{1}{2}\)

          x - \(\frac{15}{2}\)= 2

          x = 2 + \(\frac{15}{2}\)

          x = \(\frac{19}{2}\)

b, 2012 x X - 2010 x X = 2014

    ( 2012 - 2010 ) x X = 2014

              2 x X = 2014

                    X = 2014 : 2 

                    X = 1007

a) \(5+3^{x+1}=86\)

\(=>3^{x+1}=86-5\)

\(=>3^{x+1}=81=3^4\)

\(=>x+1=4\) ( cùng cơ số )

\(=>x=4-1\)

\(=>x=3\)

b) \(15:\left(x+2\right)=\left(3^3+3\right):10\)

\(=>15:\left(x+2\right)=\left(27+3\right):10\)

\(=>15:\left(x+2\right)=30:10=3\)

\(=>x+2=15:3\)

\(=>x+2=5\)

\(=>x=5-2\)

\(=>x=3\)

c) \(\left(9x+2\right).4=80\)

\(=>9x+2=80:4\)

\(=>9x+2=20\)

\(=>9x=20-2\)

\(=>9x=18\)

\(=>x=18:9\)

\(=>x=2\)

d) \(\left(245-x\right)+7^2=14\)

\(=>\left(245-x\right)+14=14\)

\(=>245-x=14-14\)

\(=>245-x=0\)

\(=>x=245-0\)

\(=>x=245\)

?

\(\frac{2}{5}.\frac{1}{x}+\frac{1}{x}.2+\frac{2}{5}=0,5\)

\(\Rightarrow\frac{2}{5x}+\frac{2}{x}+\frac{2}{5}=\frac{1}{2}\)

\(\Rightarrow2.\left(\frac{1}{5x}+\frac{1}{x}+\frac{1}{5}\right)=\frac{1}{2}\)

\(\Rightarrow\frac{1}{5x}+\frac{5}{5x}+\frac{x}{5x}=\frac{1}{2}:2=\frac{1}{4}\)

\(\Rightarrow\frac{1+5+x}{5x}=\frac{1}{4}\)

\(\Rightarrow4.\left(1+5+x\right)=5x\)

\(\Rightarrow4+20+4x=5x\)

\(\Rightarrow24+4x=5x\)

\(\Rightarrow5x-4x=24\)

\(\Rightarrow x=24\)

Trả lời

2/5.1/x+1/x.2+2/5=0,5

1/x.(2/5+2)+2/5   =1/2

1/x.12/5+2/5        =1/2

1/x.12/5               =1/2-2/5

1/x.12/5               =1/10

1/x                       =1/10:12/5

1/x                       =1/24.

Hình như mk làm sai !

\(\frac{2}{5}.\frac{1}{x}+\frac{1}{x}.2+\frac{2}{5}=0,5\)

\(\Rightarrow\frac{1}{x}\left(\frac{2}{5}+\frac{4}{2}\right)=\frac{1}{2}-\frac{2}{5}\)

\(\Rightarrow\frac{1}{x}.\frac{12}{5}=\frac{1}{10}\)

\(\Rightarrow\frac{1}{x}=\frac{1}{24}\)

\(\Rightarrow x=24\)

~Study well~

a)(3/2-0,5)/x=7/2+1/4

(3/2-1/2)/x=14/4+1/4

1/x=15/4

x=1:15/4

x=4/15

b)(x*0,25+2010)*2011=(53+2010)*(2012-1)

(x*0,25+2010)*2011=2063*2011

=>0,25x+2010=2063

0,25x=2063-2010

0,25x=53

x=53/0,25

x=212

a) \(\frac{7}{13}x\frac{7}{15}-\frac{5}{12}x\frac{21}{39}+\frac{49}{91}x\frac{8}{15}=\frac{7}{13}x\frac{7}{15}-\frac{5}{12}x\frac{7}{13}+\frac{7}{13}x\frac{8}{15}\)

\(=\frac{7}{13}x\left(\frac{7}{15}-\frac{5}{12}+\frac{8}{15}\right)=\frac{7}{13}x\left(1-\frac{5}{12}\right)=\frac{7}{13}x\frac{7}{12}=\frac{49}{156}\)

b) \(\left(\frac{12}{199}+\frac{23}{200}-\frac{34}{201}\right)x\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)=\left(\frac{12}{199}+\frac{23}{200}-\frac{34}{201}\right)x0=0\)

Bài 2:

a) \(0,5+\left(x-\frac{15}{2}\right):\frac{1}{2}=\frac{9}{2}\)

\(\left(x-\frac{15}{2}\right):\frac{1}{2}=4\)

\(x-\frac{15}{2}=2\) 

x = 19/2

b) \(2012\times x-2010\times x=2014\)

\(x\times\left(2012-2010\right)=2014\)

\(x\times2=2014\)

x = 1007

c) ( x + 1) + (x+2) + (x+3)+...+(x+100) = 5750

\(x\times100+\left(1+2+3+...+100\right)=5750\)

\(x\times100+5050=5750\)

\(x\times100=700\)

x = 7