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a: \(=-4\cdot\dfrac{2}{5}=-\dfrac{8}{5}\)

b: \(=3.6\cdot\dfrac{4}{3}=4.8\)

c: \(=72000\cdot\dfrac{3}{4}=54000\left(đồng\right)\)

16 tháng 5 2021

1/4 của 40m là:

40 : 1/4 = 160 ( m )

3/5 của 48 cm là:
48 : 3/5 = 80 ( cm )

10% của 4/5 kg là:

45 : 10 x 100= 450 ( kg )

1 và 2/13 = 15/13 ;   1 và 1/6 = 7/6 

Vậy 15/13 của 7/6 mlà:

7/6 : 15/13 = 91/90 ( m2)

Đ/s: ..........

~Hok tốt ~

25 tháng 2 2020

a, Ta có : M= 1 - 2 + 3 -4 + 5-6 +... + 19 - 20

                   = ( 1-2 ) + ( 3 - 4 ) + ( 5-6 ) + ...+ ( 19 - 20 )

                   = ( -1 ) + ( -1 )  + ( -1 ) +...+ (-1 )  ( có 10 số  ( - 1 )

                    = 10 . (-1 )

                  

25 tháng 2 2020

câu b làm sao vậy bạn

AH
Akai Haruma
Giáo viên
6 tháng 12 2023

Bài 1:

$M=3.4.5+4.5.6+...+13.14.15$

$4M=3.4.5(6-2)+4.5.6(7-3)+....+13.14.15(16-12)$

$=-2.3.4.5+3.4.5.6-3.4.5.6+4.5.6.7+....-12.13.14.15+13.14.15.16$

$=-2.3.4.5+13.14.15.16=43560$

$M=43560:4=10890$

AH
Akai Haruma
Giáo viên
6 tháng 12 2023

Bài 2:

a.

$3M=\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{97.100}$

$=\frac{4-1}{1.4}+\frac{7-4}{4.7}+\frac{10-7}{7.10}+...+\frac{100-97}{97.100}$

$=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{97}-\frac{1}{100}$

$=1-\frac{1}{100}=\frac{99}{100}$

$M=\frac{99}{100}:3=\frac{33}{100}$

6 tháng 5 2019

1. 

a) \(\frac{13}{8}:\frac{13}{4}=\frac{1}{2}=0,5=50\%\)

b) \(12,5:2,5=5=500\%\)

~ Hok tốt ~

6 tháng 5 2019

2.

\(\left(\frac{37}{9}+\frac{13}{4}\right).\frac{9}{4}+\frac{11}{4}\)

\(=\frac{265}{36}.\frac{9}{4}+\frac{11}{4}\)

\(=\frac{265}{16}+\frac{11}{4}\)

\(=\frac{309}{16}\)

\(1+\left(\frac{9}{10}-\frac{4}{5}\right):\frac{19}{6}\)

\(=1+\frac{1}{10}:\frac{19}{6}\)

\(=1+\frac{3}{95}\)

\(=\frac{98}{95}\)

\(\left(-7+\left|13\right|\right)-\left(13-\left|-7\right|-25\right)-\left(25+\left|-10\right|-9\right)\)

\(=\left(-7+13\right)-\left(13-7-25\right)-\left(25+10-9\right)\)

\(=-7+13-13+7+25-25-10+9\)

\(=\left(-7+7\right)+\left(13-13\right)+\left(25-25\right)-10+9\)

\(=0+0+0-10+9\)

\(=-10+9\)

\(=-1\)

~ Hok tốt ~

18 tháng 4 2023

\(1,-\dfrac{4}{7}+\dfrac{2}{3}\times\dfrac{-9}{14}\)

\(=\dfrac{-4}{7}+\dfrac{-18}{42}\)

\(=\dfrac{-4\times6}{7\times6}+\dfrac{-18}{42}\)

\(=\dfrac{-20}{42}+\dfrac{-18}{42}\)

\(=-\dfrac{38}{42}\)

\(=-\dfrac{19}{21}\)

\(2,\dfrac{17}{13}-\left(\dfrac{4}{13}-11\right)\)

\(=\dfrac{17}{13}-\dfrac{4}{13}+11\)

\(=\dfrac{13}{13}+11\)

\(=1+11\)

\(=12\)

\(3,8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)\)

\(=\dfrac{58}{7}-\left(\dfrac{31}{9}+\dfrac{30}{7}\right)\)

\(=\dfrac{58}{7}-\dfrac{31}{9}-\dfrac{30}{7}\)

\(=\dfrac{58}{7}-\dfrac{30}{7}-\dfrac{31}{9}\)

\(=\dfrac{28}{7}-\dfrac{31}{9}\)

\(=\dfrac{28\times9}{7\times9}-\dfrac{31\times7}{9\times7}\)

\(=\dfrac{252}{63}-\dfrac{217}{63}\)

\(=\dfrac{35}{63}\)

\(=\dfrac{5}{9}\)

\(5,\left(\dfrac{2}{3}-1\dfrac{1}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}\)

\(=\left(\dfrac{2}{3}-\dfrac{3}{2}\right):\dfrac{4}{3}+\dfrac{1}{2}\)

\(=\left(\dfrac{2\times2}{3\times2}-\dfrac{3\times3}{2\times3}\right):\dfrac{4}{3}+\dfrac{1}{2}\)

\(=\left(\dfrac{4}{6}-\dfrac{9}{6}\right):\dfrac{4}{3}+\dfrac{1}{2}\)

\(=\dfrac{-5}{6}:\dfrac{4}{3}+\dfrac{1}{2}\)

\(=\dfrac{-5}{6}\times\dfrac{3}{4}+\dfrac{1}{2}\)

\(=\dfrac{-15}{24}+\dfrac{1}{2}\)

\(=\dfrac{-15}{24}+\dfrac{1\times12}{2\times12}\)

\(=\dfrac{-15}{24}+\dfrac{12}{24}\)

\(=\dfrac{-3}{24}\)

\(=-\dfrac{1}{8}\)

\(6,\dfrac{-5}{13}+\dfrac{2}{5}+\dfrac{-8}{13}+\dfrac{3}{5}-\dfrac{3}{7}\)

\(=\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)-\dfrac{3}{7}\)

\(=\dfrac{-13}{13}+\dfrac{5}{5}-\dfrac{3}{7}\)

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

\(=-\dfrac{3}{7}\)

\(7,\dfrac{6}{5}\times\dfrac{3}{7}+\dfrac{6}{5}:\dfrac{7}{10}+\dfrac{6}{5}\)

\(=\dfrac{6}{5}\times\dfrac{3}{7}+\dfrac{6}{5}\times\dfrac{10}{7}+\dfrac{6}{5}\)

\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+1\right)\)

\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+\dfrac{1\times7}{1\times7}\right)\)

\(=\dfrac{6}{5}\times\left(\dfrac{3}{7}+\dfrac{10}{7}+\dfrac{7}{7}\right)\)

\(=\dfrac{6}{5}\times\dfrac{20}{7}\)

\(=\dfrac{120}{35}\)

\(=\dfrac{24}{7}\)

 

3: 

\(=\dfrac{1}{7}\cdot\dfrac{3}{5}\cdot\dfrac{5}{6}\cdot\dfrac{5}{8}=\dfrac{1}{7}\cdot\dfrac{1}{2}\cdot\dfrac{5}{8}=\dfrac{5}{112}\)

4:

=>2/3:x=-2-1/3=-7/3

=>x=-2/3:7/3=-2/7

5:

AC=CB=12/2=6cm

IB=6/2=3cm

7 tháng 2 2022

bạn viết cái này nó dễ hơn đó undefined

a: \(=\dfrac{-3}{7}-\dfrac{4}{7}+\dfrac{5}{13}=\dfrac{5}{13}-1=-\dfrac{8}{13}\)

b: \(=\dfrac{-5}{21}-\dfrac{2}{21}+\dfrac{1}{3}=\dfrac{-7}{21}+\dfrac{1}{3}=0\)

c: \(=\dfrac{-1}{2}+\dfrac{4}{5}+\dfrac{2}{3}-\dfrac{2}{3}+\dfrac{7}{9}\)

\(=\dfrac{-45}{90}+\dfrac{72}{90}+\dfrac{70}{90}=\dfrac{97}{90}\)

Câu 2: 

a: \(x^{10}=1^x\)

\(\Leftrightarrow x^{10}=1\)

=>x=1 hoặc x=-1

b: \(\left(2x-15\right)^5=\left(2x-15\right)^3\)

\(\Leftrightarrow\left(2x-15\right)^3\left[\left(2x-15\right)^2-1\right]=0\)

\(\Leftrightarrow\left(2x-15\right)^3\cdot\left(2x-16\right)\left(2x-14\right)=0\)

hay \(x\in\left\{\dfrac{15}{2};8;7\right\}\)

c: \(x^{10}=x\)

\(\Leftrightarrow x\left(x^9-1\right)=0\)

=>x=0 hoặc x=1