a) \(227+50+23=\left(227+23\right)+50=250+50=300\)

b) \(135+360+65+40=\left(135+65\right)+\left(360+40\right)=200+400=600\)

c) \(1+2+3+4+5+...+97+98+99+100\)

\(=\left(100+1\right)+\left(99+2\right)+...+\left(50+51\right)\)

\(=101+101+101+...+101\)

\(=101\cdot50\)

\(\Leftrightarrow5050\)

d) \(115\cdot13-13\cdot15=13\cdot\left(115-15\right)=13\cdot100=1300\)

e) \(50-49+48-47+...+4-3+2-1\)

\(=\left(50-49\right)+\left(48-47\right)+...+\left(2-1\right)\)

\(=1+1+1+1+..+1\)

\(=1\cdot25\)

\(=25\)

f) \(30\cdot40\cdot50\cdot60=10\cdot3+10\cdot4+10\cdot5+10\cdot6\)

\(=10\cdot10\cdot10\cdot10\cdot3\cdot4\cdot5\cdot6\)

\(=10000\cdot360\)

\(=3600000\)

g) \(27\cdot36+27\cdot64=27\cdot\left(36+64\right)=27\cdot100=2700\)

h) \(5\cdot2^2-18:3=5\cdot4-18:3=20-6=14\)

i) \(13\cdot17-256:16+14:7-2021^0\)

\(=13\cdot17-4^4:4^2+2-1\)

\(=13\cdot17-16+2-1\)

\(=13\cdot17-17\)

\(=17\cdot\left(13-1\right)\)

\(=204\)

j) \(7^2-36:3=49-12=37\)

Tách ít ra thôi bn.

Tách ít ra thôi bn.

8: =156x200=31200

10: =-1945-567+1945=-567

1) 2155 - (174 + 2155) + (-68 + 174)

=2155-174-2155-68+174

=(2155-2155)+(-174+174)-68

=0+0-68

=-68

2) -25 . 72 + 25 . 21 - 49 . 25

=25.(-72+21-49)

=25.(-100)

=-2500

3) 35(14 - 23) - 23(14 - 35)

=35.(-9)-23.(-21)

=(-315)-(-483)

=168

4) 8154 - (674 + 8154) + (-98 + 674)

= 8154-674-8154-98+674

=(8154-8154) + (-674+674) - 98

=0+0-98

=-98

1) 68

2) -2500

3)-88

4)-98

lấy máy tính mà tính

hihi

c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)

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

\(=1-2=-1\)

Giải:

a)-1/12+4/3=-1/12+16/12=15/12=5/4

b)(-4/14-3/15)-(1/5-20/35-(-1)).7

=-17/35-22/35.7

=-17/35-22/5

=-171/35

c)3/5+-5/20+30/75+-7/4

=3/5+-1/4+2/5+-7/4

=(3/5+2/5)+(-1/4+-7/4)

=1+-2

=-1

d)5/6.-12/14+7/13

=-5/7+7/13

=-16/91

e)2/-9-5/-36-1/4

=-1/12-1/4

=-1/3

f)2/23+-5/12+7/18+21/23+-7/12

=(2/23+21/23)+(-5/12+-7/12)+7/18

=1+-1+7/18

=7/18

xcsxccsz

a,1-2+3-4+...+49-50.

=(-1)+(-1)+...+(-1)

=-25

b,1-4+7-10+...-100+103

=(-3)+(-3)+...+(-3)+103

=(-150)+103

=-47

a) 1 - 2 + 3 - 4 + ... + 49 - 50

= -1 + (-1) + ... + (-1)

= -1 . [(50 - 1) + 1] : 2

= -1 . 25

= -25

b) 1 - 4 + 7 - 10 + ... - 100 + 103

= -3 + (-3) + ... + (-3) + 103

= -3 . [(100 - 1) : 3 + 1] : 2 + 103

= -3 . 34 : 2 + 103

= -3 . 17 + 103

= -51 + 103

= 52

= -47

tk mk nha

bn sakuura sai

\(B=1.2.3+2.3.4+3.4.5+.......+49.50.51\)

\(\Rightarrow4B=1.2.3.4+2.3.4.4+3.4.5.4+.......+49.50.51.4\)

\(=1.2.3.4+2.3.4\left(5-1\right)+3.4.5\left(6-2\right)+.........+49.50.51.\left(52-48\right)\)

\(=1.2.3.4+2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+.........+49.50.51.52-48.49.50.51\)

\(=49.50.51.52\)

\(\Rightarrow B=\frac{49.50.51.52}{4}=1624350\)

câu 1 = -68

câu 2 =-2500

câu 3=168

câu 4 =4571

câu 6=124

a: \(61\cdot45+61\cdot23-68\cdot51\)

\(=61\left(45+23\right)-68\cdot51\)

\(=68\cdot61-68\cdot51\)

\(=68\left(61-51\right)=68\cdot10=680\)

b: \(3\cdot5^2-\left(75-4\cdot2^3\right)\)

\(=75-75+4\cdot8\)

\(=4\cdot8=32\)

c: \(36:\left\{2^2\cdot5-\left[30-\left(5-1\right)^2\right]\right\}\)

\(=\dfrac{36}{20-30+4^2}\)

\(=\dfrac{36}{-10+16}=\dfrac{36}{6}=6\)

d: \(\left(12\cdot49-3\cdot2^2\cdot7^2\right):\left(2020\cdot2021\right)\)

\(=\dfrac{\left(12\cdot49-12\cdot49\right)}{2020\cdot2021}=0\)