25-2 : (3/5-1/2) + (5/2 +1/5 * 1/4 )

= 25 - 2 : 1/10 + (5/2 + 1/20)

= 25 - 20 + 51/20

= 5 + 51/20

= \(5\frac{51}{20}\)

( 3/10+ 4/5 *1/2 ) : (17/9 -4/3 : 3)

= (3/10 + 2/5) : (17/9 - 4/9)

= (-1/10) : 13/9

= -9/130

`@` `\text {Ans}`

`\downarrow`

`1/3+6/9+4/5+5/25`

`= 1/3+2/3+4/5+1/5`

`= 1+1`

`= 2`

`4/7*2/5+4/7*3/5-1/7`

`= 4/7*(2/5+3/5)-1/7`

`= 4/7*1-1/7`

`= 4/7-1/7=3/7`

.....................................................

a) 1+2+3+...+2018

=[(2018-1):1+1].(2018+1):2

=2018.2019:2

=2037171

b) 4+7+10+13+...+2017

=[(2017-4):3+1].(2017+4):2

=672.2021:2

=679056

c) 1+2-3-4+5+6-7-8+9+10-11-12+13+14

=(1+2-3-4)+(5+6-7-8)+(9+10-11-12)+13+14

=-4+(-4)+(-4)+13+14

=-12+27

=15

d) 23 x 75 + 25 x 23 + 180

=23 x (75+25) +180

=23 x 100 +180

=2300+180

2480

chúc ban hoc tốt nha

a) Số số hạng: ( 2018 - 1 ) : 1 + 1 = 2018

   Tổng:           2018 x ( 2018 + 1 ) : 2 = 2 037 171

a) 3 2/7 - 2/5 + 5/7 - 3/5

= 3 + 2/7 - (2/5 + 3/5) + 5/7

= 3 + (2/7 + 5/7) - 1

= 3 + 1 - 1

= 3

b) 5 4/7 - 4/9 + 1 3/7 - 5/9

= 5 + 4/7 - 4/9 + 1 + 3/7 - 5/9

= (5 + 1) + (4/7 + 3/7) - (4/9 + 5/9)

= 6 + 1 - 1

= 6

a) \(3\dfrac{2}{7}-\dfrac{2}{5}+\dfrac{5}{7}-\dfrac{3}{5}\)

\(=\left(\dfrac{23}{7}+\dfrac{5}{7}\right)-\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\)

\(=4-1\)

\(=3\)

b) \(5\dfrac{4}{7}-\dfrac{4}{9}+1\dfrac{3}{7}-\dfrac{5}{9}\)

\(=\left(\dfrac{32}{7}+\dfrac{10}{7}\right)-\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)

\(=6-1\)

\(=5\)

c \(\dfrac{2}{3}\times\dfrac{13}{4}\times\dfrac{3}{2}\times\dfrac{7}{3}\times\dfrac{4}{7}\)

= \(\dfrac{2\times13\times3\times7\times4}{3\times4\times2\times3\times7}\)

= \(\dfrac{13}{3}\)

\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}\)

=\(\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}\)

=\(\dfrac{1}{1}-\dfrac{1}{5}\)

=\(\dfrac{4}{5}\)

a, (\(\dfrac{41}{25}\) + \(\dfrac{17}{100}\)) + \(\dfrac{39}{25}\)

= (\(\dfrac{41}{25}\) + \(\dfrac{39}{25}\)) + \(\dfrac{17}{100}\) 

= \(\dfrac{80}{25}\) + \(\dfrac{17}{100}\)

= \(\dfrac{320}{100}\) + \(\dfrac{17}{100}\)

= \(\dfrac{337}{100}\)

g, \(\dfrac{1}{12}\) + \(\dfrac{1}{20}\) + \(\dfrac{1}{30}\) + \(\dfrac{1}{42}\)

= \(\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}\)

= \(\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\)

= \(\dfrac{1}{3}-\dfrac{1}{7}\)

= \(\dfrac{7}{21}-\dfrac{3}{21}\)

= \(\dfrac{4}{21}\)

a; 5\(\dfrac{3}{4}\) : 3 + 2\(\dfrac{1}{4}\).\(\dfrac{1}{3}\) - \(\dfrac{3}{8}\)

= \(\dfrac{23}{4}\) : 3 + \(\dfrac{9}{4}\).\(\dfrac{1}{3}\) - \(\dfrac{3}{8}\)

= \(\dfrac{23}{4}\) x \(\dfrac{1}{3}\) + \(\dfrac{3}{4}\) - \(\dfrac{3}{8}\)

= \(\dfrac{23}{12}\) + \(\dfrac{3}{4}\) - \(\dfrac{3}{8}\)

= \(\dfrac{46}{24}\) + \(\dfrac{18}{24}\) - \(\dfrac{9}{24}\)

= \(\dfrac{64}{24}\) - \(\dfrac{9}{24}\)

= \(\dfrac{55}{24}\)

(dấu . là dấu nhân )

a, \(\frac{3}{2}\cdot\frac{4}{7}+\frac{3}{7}\cdot\frac{3}{2}\)

= \(\frac{3}{2}\left(\frac{4}{7}+\frac{3}{7}\right)\)

=\(\frac{3}{2}\cdot\frac{7}{7}=\frac{3}{2}\)

b, \(\frac{12}{5}\cdot4-4\cdot\frac{7}{5}\)

=\(4\left(\frac{12}{5}-\frac{7}{5}\right)=4\cdot\frac{5}{5}=4\)

c, \(\frac{5}{11}:\frac{1}{2}+\frac{6}{11}:\frac{1}{2}\)

=\(2\left(\frac{5}{11}+\frac{6}{11}\right)=2\cdot\frac{11}{11}=2\)

a;3/2x(4/7+3/7)

=3/2x1

=3/2

b;12/5x4-4x7/5

=4x(12/5-7/5)

=4x1

=4

c;5/11:1/2+6/11:1/2

=1/2:(5/11+6/11)

=1/2:1

=1/2

\(\frac{9}{2}\) \(-\) (  \(x\) \(-\) \(\frac{3}{4}\) )   =  \(\frac{25}{4}\)

                      \(x\) \(-\) \(\frac{3}{4}\)      =   \(\frac{9}{2}\) \(-\) \(\frac{25}{4}\)

                      \(x\)  \(-\) \(\frac{3}{4}\)    =  \(-\frac{7}{4}\)

                                   \(x\)           =    \(-\frac{7}{4}\) \(+\)  \(\frac{3}{4}\) 

                                   \(x\)           =      \(-1\)

\(4\) \(+\) \(x\) \(+\) \(\frac{3}{4}\)     =  \(\frac{17}{2}\)

(  \(4\) \(+\) \(\frac{3}{4}\))  \(+\)\(x\) =     \(\frac{17}{2}\)

      \(\frac{19}{4}\)      \(+\)    \(x\)      =      \(\frac{17}{2}\)

                                 \(x\)         =    \(\frac{17}{2}\) \(-\)    \(\frac{19}{4}\) 

                               \(x\)          =  \(\frac{15}{4}\)