1) 2x – (3 – 5x) = 4( x +3)

<=>2x-3+5x=4x+12

<=>2x-3+5x-4x-12=0

<=>3x-15=0

<=>x=5

2) 5(2x-3) - 4(5x-7) =19 - 2(x+11)

<=>10x-15-20x+28=19-2x-22

<=>10x-15-20x+28-19+2x+22=0

<=>-8x+16=0

<=>x=2

Bài 1:

a: Cách 1: \(\left(\frac23-\frac45\right)\times25\)

\(=\left(\frac{10}{15}-\frac{12}{25}\right)\times25\)

\(=-\frac{2}{25}\times15=-\frac{30}{15}=-\frac65\)

Cách 2: \(\left(\frac23-\frac45\right)\times25\)

\(=\frac23\times25-\frac45\times25\)

\(=\frac{50}{3}-20=\frac{50}{3}-\frac{100}{5}=\frac{50}{3}-20=\frac{50}{3}-\frac{60}{3}=-\frac{10}{3}\)

b: Sửa đề: \(\frac34\times\frac25+\frac34\times\frac27\)

Cách 1: \(\frac34\times\frac25+\frac34\times\frac27\)

\(=\frac34\times\left(\frac25+\frac27\right)\)

\(=\frac34\times\left(\frac{14}{35}+\frac{10}{35}\right)\)

\(=\frac34\times\frac{24}{35}=\frac{72}{140}=\frac{18}{35}\)

Cách 2:

\(\frac34\times\frac25+\frac34\times\frac27\)

\(=\frac{6}{20}+\frac{6}{28}\)

\(=\frac{42}{140}+\frac{30}{140}=\frac{72}{140}=\frac{18}{35}\)

Bài 2:

a: \(x:\frac25=\frac23\)

=>\(x=\frac23\times\frac25=\frac{4}{15}\)

b: \(x:\frac23=\frac49\)

=>\(x=\frac49\times\frac23=\frac{8}{27}\)

a)

b)

c)

d)

Tớ chưa học đến

cái này ai cũng học rùi mà

a)\(=\dfrac{16}{13}-\dfrac{3}{15}+\dfrac{6}{13}=\dfrac{22}{13}-\dfrac{3}{15}=\dfrac{96}{65}\)

b)\(=\dfrac{21}{8}-\left(\dfrac{5}{10}+\dfrac{6}{10}\right)=\dfrac{21}{8}-\dfrac{11}{10}=\dfrac{61}{40}\)

c)\(=\dfrac{27}{10}-3-\dfrac{4}{7}--\dfrac{61}{70}\)

d)\(=\dfrac{576}{702}=\dfrac{4}{5}\)

e)\(=\left(\dfrac{20}{15}-\dfrac{12}{15}\right)\times\dfrac{25}{2}=\dfrac{8}{15}\times\dfrac{25}{2}=\dfrac{20}{3}\)

f)\(=\dfrac{24}{12}-\dfrac{4}{12}-\dfrac{6}{12}-\dfrac{2}{12}-\dfrac{3}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)

a) \(A=\left\{22;23;24;25\right\}\)

b) \(B=\left\{0;1;2;3\right\}\)

c) \(C=\left\{14;16;18;20;22;24\right\}\)

d) \(D=\left\{1;3\right\}\)

4 × 125 × 25 × 8

= (4 × 25) × (125 × 8)

= 100 × 1000

= 100 000

2 × 8 × 50 × 25 × 125

= (2 × 50) × (8 × 125) × 25

= 100 × 1000 × 125

= 12 500 000

2 × 3 × 4 × 5 × 50 × 25

= (2 × 50) × (4 × 25) × (3 × 5)

= 100 × 100 × 15

= 150 000

25 × 20 × 125 × 8 - 8 × 20 × 5 × 125

= 8 × 125 × 20 × (25 - 5)

= 1000 × 20 × 20

= 400 000

- (25 x 4) x (125 x8)=100 x 1000 =100000

- (50 x 2) x (8 x 125) x 25=100 x 1000 x 25 =2500000

- (2 x 50 ) x (4 x 25) x (3 x5)=100 x 100 x 15=150000

- 25 x 20 x125 x 8 - 5

= (20 x 5) x (125 x 8) -25=100 x 1000 -5 =100000 - 5 =99995

a) \(\frac{15}{9}:\frac{3}{4}:\frac{7}{5}=\frac{15}{9}.\frac{4}{3}.\frac{5}{7}=\frac{300}{189}=\frac{100}{63}\)

b ) \(\frac{23}{7}.\frac{25}{2}-\frac{23}{7}.\left(5+\frac{1}{2}\right)=\frac{23}{7}.\left(\frac{25}{2}-\frac{11}{2}\right)=\frac{23}{7}.7=23\)

a)\(\frac{100}{63}\)

b)   23

\(4^2-2^2.3+8.5^0\)

\(=16-4.3+8.1\)

\(=12\)

\(5^4.\left[8^2:4^2.\left(2^3+10^0\right)\right]\)

\(=625.\left[64:16.\left(8+1\right)\right]\)

\(=625.\left(64:16.9\right)\)

\(=22500\)

\(11^2.5^3-11^2.25\)

\(=11^2.\left(5^3-25\right)\)

\(=121.\left(125-25\right)\)

\(=12100\)

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