a) `123 - 27 + 27 + 13 - 123`

`= (123 - 123) + (27 - 27) + 13`

`= 0 + 0 + 13`

`= 13`

`---`

b) `175 + 25 + 13 + 15 - 175 - 25`

`= (175-175)+(25-25)+25+13`

`=0+0+25+13`

`=28`

`---`

c) \(53\times39+47\times39+53\times21+47\times21\)

\(=\text{[}\left(53+47\right)\times39]+\left[\left(53+47\right)\times21\right]\)

\(=\left(100\times39\right)+\left(100\times21\right)\)

\(=3900+2100\)

`=6000`

`---`

d) \(49\times35+49\times16-49\times61\)

`=` \(49\times\left(35+16-61\right)\)

`=` \(49\times\left(-10\right)\)

`=-490`

Bài 1:

a. A = 125 . (-61) . (-2)³ . (-1)²⁴

= 125. (-8). (-61) . 1²⁴

= 125. 8. 61.1

= 1000. 61 = 61000

b. B = 136. (-47) + 36.47

= (-136).47 + 36.47

= 47. (-136 + 36)

= 47. (-100) = -4700

c. C = (-48).72 + 36.(-304)

= (-96).36 + 36. (-304)

= 36. (-96-304)

= 36. (-400) = -14400

d. D = 87.(13-18) - 13.(87 + 18)

= 87.13 - 87.18 - 13.87 - 13.18

= - 87.18 - 18.13

= - 18.(87+13)

= - 18.100 = -1800

Bài 2:

a. TH1: x - 2 = 0 => x = 2

TH2: 5-x = 0 => x = 5

b. |x| = 56 - 23 = 33 => x = cộng trừ 33

c. 3 - (17-x) = 289 - (36 + 289)

=> 3 - 17 + x = 289 - 289 - 36

=> -14 + x = -36

=> x = -36 - (-14) = -22

1. 

a. A = 125 . (-61) . (-2)³ . (-1)²⁴ 

= 125.(-61).(-8).1

= (-8.125).(-61)

= -1000.(-61)

= 61000

b. B = 136 . (-47) + 36 . 47 

=-136.47+36.47

=47(-136+36)

= 47.(-100)

= -4700

2. 

a. (x - 2) . (5 - x) = 0

=> x - 2 = 0 hoặc 5 - x = 0

=> x = 2 hoặc x = 5

b. 56 - lxl = 23 

=> |x| = 33

=> x = 33 hoặc x = -33

c. 3 - (17 - x) = 289 - (36 + 289) 

=> 3 - 17 + x = 289 - 36 - 289

=> -14 + x = -36

=> x = -22

11 x 13 x 15 x 17 + 23 x 25 x 27 x 29 + 31 x 33 x 35 x 37 + 45 x 47 x 49 x 51

=7096860

#Hok tốt!#

c/s 0

Bài 1: 

a) Ta có: 49+(11-25)

=49+11-25

=24+11

=35

b) Ta có: \(-8+5\cdot\left(-9\right)\)

\(=-8-45\)

=-53

Bài 2: 

a) Ta có: \(x-2=-6+17\)

\(\Leftrightarrow x-2=11\)

hay x=13

Vậy: x=13

b) Ta có: \(x+9=2-17\)

\(\Leftrightarrow x+9=-15\)

hay x=-24

Vậy: x=-24

a) \(\left(145\times99+145\right)-\left(143\times102-143\right)\)

\(=\left[145\times\left(99+1\right)\right]-\left[143\times\left(102-1\right)\right]\)

\(=\left(145\times100\right)-\left(143\times101\right)\)

\(=14500-14443\)

\(=57\)

b) \(54\times47-47\times53-20-27\)

\(=47\times\left(54-53\right)-20-27\)

\(=47-20-27\)

\(=0\)

c) \(10000-47\times72-47\times28\)

\(=10000-47\times\left(72+28\right)\)

\(=10000-47\times100\)

\(=10000-4700\)

\(=5300\)

d) \(3457-27\times48-48\times73+6543\)

\(=\left(3457+6543\right)-48\times\left(27+73\right)\)

\(=10000-48\times100\)

\(=10000-4800\)

\(=5200\)

a: \(=68\cdot72\cdot49\cdot\left[324-324\right]=0\)

b: \(=\left(1250-1250\right)\cdot\left(1+...+100\right)=0\)

\(a,\left(68\times72\times49\right)\times\left(27\times12-9\times36\right)=\left(68\times72\times49\right)\times0=0\\ b,\left(25\times50-125\times10\right)\times\left(1+2+...+100\right)=0\times\left(1+2+...+100\right)=0\)

a, ( 68 × 72 × 49 ) × ( 27 × 12 − 9 × 36 ) = ( 68 × 72 × 49 ) × 0 =

b, ( 25 × 50 − 125 × 10 ) × ( 1 + 2 + ... + 100 ) = 0 × ( 1 + 2 + ... + 100 ) = 0

1000 - 47 . 72 - 47 .28

= 47 . ( 1000 - 72 -28 )

= 47 .0

=0

3457 - 27 . 48 - 48 .73 + 6543

=3457 - 48 . (27 + 73 ) + 6543

= 3457 - 4800 + 6543

= 5200