8: =>2x=210

hay x=105

6567578.X.6567578.Y:6098+6099+......+10000=200000000

1)

a) 2x + 5 = 3⁴ : 3²

2x + 5 = 3²

2x + 5 = 9

2x = 9 - 5

2x = 4

x = 4 : 2

x = 2

b) (3x - 24).73 = 2.74

(3x - 24).73 = 148

3x - 24 = 148/73

3x = 148/73 + 24

3x = 1900/73

x = 1900/73 : 3

x = 1900/219

c) [3.(42 - x)] + 15 = 23.3

126 - 3x + 15 = 69

141 - 3x = 69

3x = 141 - 69

3x = 72

x = 72 : 3

x = 24

d) 126 + (132 - x) = 300

132 - x = 300 - 126

132 - x = 174

x = 132 - 174

x = -42

2)

a) 120 - (x + 55) = 60

x + 55 = 120 - 60

x + 155 = 60

x = 60 - 55

x = 5

b) (7x - 11).3 = 25.52 + 200

(7x - 11).3 = 1500

7x - 11 = 1500 : 3

7x - 11 = 500

7x = 500 + 11

7x = 511

x = 511 : 7

x = 73

c) 2x + 2x + 4 = 544

4x = 544 - 4

4x = 540

x = 540 : 4

x = 135

3) 

a) 10 + 2x = 49 : 47

10 + 2x = 49/47

2x = 49/47 - 10

2x = -421/47

x = -421/47 : 2

x = -421/94

b) 70 - 5(x - 3) = 45

5(x - 3) = 70 - 45

5(x - 3) = 25

x - 3 = 25 : 5

x - 3 = 5

x = 5 + 3

x = 8

c) 4 + 95 : x = 143 : 142 - 23

4 + 95 : x = -3123/142

95 : x = -3123/142 - 4

95 : x = -3691/142

x = 95 : (-3691/142)

x = -13490/3691

cau1 :120-(100+x)=25

100+x=120-25

100+x=95

x=-5

cau2: 5(x+23)+6=96

5(x+23)+6=96

5(x+23)=90

x+23=18

x=-5

cau3: 100-(25+x)=40

25+x=100-40

25+x=60

x=35

cau4: 35-9(x+2)=45

9(x+2)=-10

x+2=-10/9

x=-28/9

cau 4 cua ban ghi gi minh ko  hieu

= 230

= 196490

= 36000
 

23 + 23 x 2 + 23 x 3 + 23 x 4

= 23 x (1 + 2 + 3 + 4)

= 23 x 10

= 230

246 x 2005 - 2005 x 148

= (246 - 148) x 2005

= 98 x 2005

= 196490

25 x 12 x 30 x 4

= (25 x 4) x 12 x 30

= 100 x 360

= 36000

  233 + 23 x 2 + 23 x 3 + 23 x 4

= 23 x ( 1 + 2 + 3 + 4 )

= 23 x 10

= 230

  246 x 2005 - 2005 x 148

= ( 246 - 148 ) x 2005 

= 98 x 2005

= 196490

  25 x 12 x 30 x 4 

= ( 25 x 4 ) x ( 12 x 30 )

= 100 x 360

= 36000

Đáp án cần chọn là: D

\(a.\dfrac{12+x}{42}=\dfrac{35}{42}\Leftrightarrow12+x=35\Leftrightarrow x=23\)

\(b.\dfrac{25-x}{40}=\dfrac{3}{8}\Leftrightarrow\dfrac{25-x}{40}=\dfrac{15}{40}\Leftrightarrow25-x=15\Leftrightarrow x=10\)

\(c.\dfrac{13+x}{20}=\dfrac{3}{4}\Leftrightarrow\dfrac{13+x}{20}=\dfrac{15}{20}\Leftrightarrow13+x=15\Leftrightarrow x=2\)

\(d.\dfrac{23-x}{25}=\dfrac{20}{25}\Leftrightarrow23-x=20\Leftrightarrow x=3\)

a. 246 x 2005 - 2005 x 148

= (246 - 148) x 2005

= 98 x 2005

= 196490

b. 25 x 12 x 30 x 4

= (25 x 4) x 12 x 30

= 100 x 360

= 36000

c. 23 + 23 x 2 + 23 x 3 + 23 x 4

= 23 x 1 + 23 x 2 + 23 x 3 + 23 x 4

= 23 x (1 + 2 + 3 + 4)

= 23 x 10

= 230

230 nhé

a, 246x2005-2005x148

=(246-148)x2005

=98x2005

=196490

b, 25x12x30x4

=(25x4)x(12x30)

=100x360

=36000

c, 23+23x2+23x3+23x4

=23x(1+2+3+4)

=23x10

=230

TL: 

8/15 x 5/6 = 40/90 = 4/9 

41/20 x 3/4 = 123/80 

(11/23 + 9/23) + (18/23 + 2/23) = 20/23 + 20/23 = 40/43 

HT

\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\) = \(\frac{2}{3}\times\frac{4}{5}\times\frac{5}{6}\)=\(\frac{2\times4\times5}{3\times5\times6}\)=\(\frac{2\times4\times5}{3\times5\times2\times3}\)=\(\frac{4}{9}\)

\(\frac{11}{23}+\frac{2}{23}+\frac{9}{23}+\frac{18}{23}\)=\(\frac{\left(11+9\right)+\left(18+2\right)}{23}\)=\(\frac{20+20}{23}\)=\(\frac{40}{23}\)

\(\frac{27}{12}+\frac{17}{6}-\frac{25}{36}-\frac{15}{6}\)=\(\left(\frac{27}{12}-\frac{25}{36}\right)+\left(\frac{17}{6}-\frac{15}{6}\right)\)=\(\frac{14}{9}+\frac{2}{6}\)=\(\frac{17}{9}\)

/HT\

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