1)

2/5x3/4+3/4x3/5

= 3/10+9/20

=6/20+9/20

=3/4

 1)

2/5x3/4+3/4x3/5

= 3/10+9/20

=6/20+9/20

2)

= 41/50-8/25

=41/50-16/50

=1/2

3)

=4/3-10/9

=12/9-10/9

=2/9

=3/4

                                               ngan:3

1) Ta có: \(\left(-\dfrac{2}{3}\right)^2\cdot\dfrac{-9}{8}-25\%\cdot\dfrac{-16}{5}\)

\(=\dfrac{4}{9}\cdot\dfrac{-9}{8}-\dfrac{1}{4}\cdot\dfrac{-16}{5}\)

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

\(=\dfrac{-5}{10}+\dfrac{8}{10}=\dfrac{3}{10}\)

2) Ta có: \(-1\dfrac{2}{5}\cdot75\%+\dfrac{-7}{5}\cdot25\%\)

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

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

3) Ta có: \(-2\dfrac{3}{7}\cdot\left(-125\%\right)+\dfrac{-17}{7}\cdot25\%\)

\(=\dfrac{-17}{7}\cdot\dfrac{-5}{4}+\dfrac{-17}{7}\cdot\dfrac{1}{4}\)

\(=\dfrac{-17}{7}\cdot\left(\dfrac{-5}{4}+\dfrac{1}{4}\right)\)

\(=\dfrac{17}{7}\)

4) Ta có: \(\left(-2\right)^3\cdot\left(\dfrac{3}{4}\cdot0.25\right):\left(2\dfrac{1}{4}-1\dfrac{1}{6}\right)\)

\(=\left(-8\right)\cdot\left(\dfrac{3}{4}\cdot\dfrac{1}{4}\right):\left(\dfrac{9}{4}-\dfrac{7}{6}\right)\)

\(=\left(-8\right)\cdot\dfrac{3}{16}:\dfrac{54-28}{24}\)

\(=\dfrac{-3}{2}\cdot\dfrac{24}{26}\)

\(=\dfrac{-72}{52}=\dfrac{-18}{13}\)

x-7=-5

=>x=-5+7=2

x+2=0

=>x=0-2=-2

\(\left(3x-2^4\right)\cdot7^3=2\cdot7^4\)

=>\(3x-16=\frac{2\cdot7^4}{7^3}=2\cdot7=14\)

=>3x=16+14=30

=>x=30/3=10

|x-5|=|-7|

=>x-5=7 hoặc x-5=-7

=>x=12 hoặc x=-2

x-[42+(-28)]=-8

=>x-14=-8

=>x=-8+14

=>x=6

128-3(x+4)=23

=>3(x+4)=128-23=105

=>x+4=35

=>x=35-4=31

4-(7-x)=x-(13-4)

=>4-7+x=x-9

=>x-3=x-9

=>-3=-9(vô lý)

=>x∈∅

Bài 2:

S1=1+2+...+999

\(=\frac{999\left(999+1\right)}{2}=999\cdot\frac{1000}{2}\)

\(=999\cdot500=499500\)

S1=10+12+...+2010

Số số hạng của dãy là:

(2010-10):2+1=2000:2+1=1001(số)

Tổng của dãy số là:

\(S_1=\left(2010+10\right)\cdot\frac{1001}{2}=2020\cdot\frac{1001}{2}=1001\cdot1010=1011010\)

Ai biết chỉ mình nha 

1. 11(x-9)=77

x-9=7

x=16

2. 4(x-3)=48

x-3=12

x=15

3.3(x-8)=81

(x-8)=27

x=35

a: \(=\dfrac{5}{4}\cdot\dfrac{2}{5}\cdot\dfrac{17}{21}\cdot\dfrac{7}{34}=\dfrac{1}{2}\cdot\dfrac{1}{2}\cdot\dfrac{1}{3}=\dfrac{1}{12}\)

b: =>0,5^x(0,5+1)=1,5

=>0,5^x=1

=>x=0

c: =>x*0,05-0,25*x=-1,2

=>-0,3*x=-1,2

=>x=4

d: =>x-1=1 hoặc x-1=-1

=>x=0 hoặc x=2

e: =5+4=9

tìm x biết:

(3x-1) [- 1/2x+5]=0

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

[2x+3/5]² - 9/25=0

-5(x+1/5)-1/2(x-2/3)=3/2x - 5 /6

[x+1/2]x [2/3-2x]=0

17/2-|2x-3/4|=-7/4

2/3x-1/2x =5/12

(x+1/5)²+17/25=26/25

[x.44/7+3/7].11/5-3/7=-2

3[3x-1/2]+1/9=0

Toán lớp 6Tìm x

 Trả lời  Câu hỏi tương tự

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3(3x-1/2)^3+1/9=0

Tìm X

a) \(2x+\dfrac{3}{24}=3x-\dfrac{1}{32}\)

\(\Leftrightarrow\left(2x+\dfrac{3}{24}\right)-\left(3x-\dfrac{1}{32}\right)=0\)

\(\Leftrightarrow2x+\dfrac{3}{24}-3x+\dfrac{1}{32}=0\)

\(\Leftrightarrow\left(\dfrac{3}{24}+\dfrac{1}{32}\right)+\left(2x-3x\right)=0\)

\(\Leftrightarrow\dfrac{5}{32}-x=0\)

\(\Leftrightarrow x=\dfrac{5}{32}\)