tổng trên có số số hạng là:

(10-0,5):0,5+1=20(số)

tổng trên là:

(10+0,5)*20:2=105

đáp số:..

phải như thế này mới đúng:

ghi đề bài

=(10+0,5)+(9,5+1)+(9+1,5)+.....+(6+5,5)

=10,5x10(số cặp)=150

a) 1/5 - (1/2 + 3/4 ) : 5/2

= 1/5 - ( 1/4 + 3/4 ) : 5/2

=1/5 - 1 : 5/2

= 1/5 - 1 . 2/5

= 1/5 - 2/5

= -1/5

b) 1,5 . (1/3 - 2/3)

=3/2 . ( -1/3)

=-1/2

c) 9/10 . 23/11 - 1/11 . 9/10 + 9/10

= 9/10 . ( 23/11 - 1/11 ) + 9/10

= 9/10 . 1 + 9/10

= 9/10 + 9/10

= 18/10 = 9/5

a, \(\Leftrightarrow2x^2=72\)

\(\Leftrightarrow x^2=36\)

\(\Leftrightarrow x=\pm6\)

Vậy ...

\(b,\Leftrightarrow\dfrac{3}{5}x-0,75=2\dfrac{4}{5}.\dfrac{3}{7}=\dfrac{6}{5}\)

\(\Leftrightarrow\dfrac{3}{5}x=\dfrac{6}{5}+0,75=\dfrac{39}{20}\)

\(\Leftrightarrow x=\dfrac{39}{20}:\dfrac{3}{5}=\dfrac{13}{4}\)

Vậy ...

\(c,\Leftrightarrow2x=1\dfrac{5}{6}.\dfrac{6}{11}-\dfrac{3}{10}=\dfrac{7}{10}\)

\(\Leftrightarrow x=\dfrac{7}{10}:2=\dfrac{7}{20}\)

Vậy ...

\(d,\Leftrightarrow\dfrac{1}{x-7\dfrac{1}{3}}=1.5:2\dfrac{1}{4}=\dfrac{2}{3}\)

\(\Leftrightarrow x-7\dfrac{1}{3}=\dfrac{3}{2}\)

\(\Leftrightarrow x=\dfrac{3}{2}+7\dfrac{1}{3}=\dfrac{53}{6}\)

Vậy ...

a) 2x² - 72 = 0

\(\Rightarrow\) 2x² = 72

\(\Rightarrow\) x² = 36 = 6² = (- 6)²

\(\Rightarrow\) x = 6 hoặc x = - 6

Vậy x = 6 hoặc x = - 6

b) (\(\dfrac{3}{5}\)x - 0,75) : \(\dfrac{3}{7}\) = \(2\dfrac{4}{5}\)

\(\Rightarrow\)  (\(\dfrac{3}{5}\)x - 0,75) : \(\dfrac{3}{7}\) = \(\dfrac{14}{5}\)

\(\Rightarrow\)  \(\dfrac{3}{5}\)x - \(\dfrac{3}{4}\) = \(\dfrac{6}{5}\)

\(\Rightarrow\) \(\dfrac{3}{5}\)x = \(\dfrac{39}{20}\)

\(\Rightarrow\) x = \(\dfrac{13}{4}\)

Vậy x = \(\dfrac{13}{4}\)

c) \(2x+\dfrac{3}{10}=1\dfrac{5}{6}.\dfrac{6}{11}\)

\(\Rightarrow\) \(2x+\dfrac{3}{10}=\dfrac{11}{6}.\dfrac{6}{11}=1\)

\(\Rightarrow\) \(2x=\dfrac{7}{10}\)

\(\Rightarrow\) \(x=\dfrac{7}{20}\)

Vậy \(x=\dfrac{7}{20}\)

d) \(2\dfrac{1}{4}:\left(x-7\dfrac{1}{3}\right)=1,5\)

\(\Rightarrow\) \(\dfrac{9}{4}:\left(x-\dfrac{22}{3}\right)=\dfrac{3}{2}\)

\(\Rightarrow\) \(x-\dfrac{22}{3}=\dfrac{3}{2}\)

\(\Rightarrow\) \(x=\dfrac{53}{6}\)

Vậy \(x=\dfrac{53}{6}\)

a: =2/3+1/5*10/7

=2/3+2/7

=14/21+6/21=20/21

b: \(=\dfrac{1}{2}\cdot\dfrac{-3+2}{4}=\dfrac{1}{2}\cdot\dfrac{-1}{4}=\dfrac{-1}{8}\)

c: \(=\dfrac{3}{4}+\dfrac{9}{5}:\dfrac{3}{2}-1\)

=-1/4+9/5*2/3

=-1/4+18/15

=-1/4+6/5

=-5/20+24/20=19/20

d: \(=\dfrac{3}{2}\cdot\left(\dfrac{7}{3}-\dfrac{5}{3}\cdot4\right)\)

\(=\dfrac{7}{2}-\dfrac{5}{2}\cdot4=\dfrac{7}{2}-\dfrac{20}{2}=\dfrac{-13}{2}\)

a: =>1/3:x=3/5-2/3=9/15-10/15=-1/15

=>x=-1/3:1/15=5

b: \(\Leftrightarrow x\cdot\dfrac{2}{3}-3=\dfrac{2}{5}\cdot\left(-10\right)=-4\)

=>x*2/3=-1

=>x=-3/2

c: =>2x+1=4 hoặc 2x+1=-4

=>x=3/2 hoặc x=-5/2

h: =>x-3=4

=>x=7

g: =>2x-1=3

=>2x=4

=>x=2

f: \(\Leftrightarrow x\cdot\left(\dfrac{3}{2}-\dfrac{7}{3}\right)=\dfrac{3}{2}-\dfrac{2}{3}\)

=>x*-5/6=5/6

=>x=-1

d: =>|2x-1|=3

=>2x-1=3 hoặc 2x-1=-3

=>x=-1 hoặc x=2

\(\dfrac{12}{15}-\dfrac{7}{10}=\dfrac{24}{30}-\dfrac{21}{30}=\dfrac{3}{30}=\dfrac{1}{10}\)
\(\dfrac{9}{14}-\dfrac{2}{7}=\dfrac{9}{14}-\dfrac{4}{14}=\dfrac{5}{14}\)
\(2-\dfrac{3}{4}=\dfrac{8}{4}-\dfrac{3}{4}=\dfrac{5}{4}\)
\(5-1,5-1\dfrac{1}{2}=5-1,5-1,5=2\)

a) X + 1/4 = 5/8 + 2/5

X + 1/4 = 41/10

X = 41/10 - 1/4

X = 31/40

b) X : 3/4 = 4/10 - 4/10

X : 3/4 = 0

X = 0

c) X + 3,4 x 2,6 = 4,8 x 5,2 

X + 8,84 = 24,96

X = 24,96 : 8,84

X = 48/17

d) X : 1,5 + 1,5 = 0,8N x 2 

= bó tay nhé