`a) 127 + 29 + 73`

`= (127+73)+29`

`= 200 + 29`

`= 229`

`c) 135 + 360 + 65 + 40`

`= (135+65)+(360+40)`

`= 200+400`

`= 600`

`c) 417-17-299`

`= (417-17)-299`

`= 400 - 299`

`= 101`

`d) 981-781+29`

`= (981-781)+29`

`= 200 + 29`

`= 229`

a) 127 + 29 + 73 = 229

b) 135 + 360 + 65 + 40 = 600

c) 417 - 17 - 299 = 104

d) 981 - 781 + 29 = 229

Chúc bạn học tốt!! ^^

a)

(-12)(-13)+13(-22) = 12.13 - 13.22 = 13(12-22)=13.(-10)=-130

b) 15(-14) +15(-6) + (-20).25 = 15[(-14)+(-6)]+(-20).25=15.(-20)+(-20).25=(-20)(15+25)=-20.40=-800

c) -65.(87-17)-87(17-65) = 

a)(-12).(-13)+13.(-22)=12.13+13.(-22)=13.[12+(-22)]=13.(-10)=-130

b)15.(-14)+15.(-6)+(-20).25=15.[(-14)+(-6)]+(-20).25=15.(-20)+(-20).25=(-20).(15+25)=(-20).40=-800

c)-65.(87-17)-87.(17-65)=-65.87-(-65).17-87.17+87.65

=-65.87+65.17-87.17+87.65

=[(-65)+65].87+(65-87).17

=0.87+(-22).17

=0+(-374)=-374

A = 78 x 31 + 78 x 24 + 78 x 17 + 22 x 72

A = 78 x ( 31 + 24 + 17 ) + 22 x 72

A = 78 x 72 + 22 x 72

A = 72 x ( 78 + 22 ) 

A = 72 x 100

A = 7200

C = 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21

C = 39 x ( 53 + 47 ) - 21 x ( 53 - 47 )

C = 39 x 100 - 21 x 6

C = 3900 - 126

C = 3774

ko pc tui thua bn 1 lp 

Số các số hạng là:(81-1):8+1=11 số

Tổng là:(81+1)x11:2=451

1 + 9 + 17 + 25 + 33 + 41 + 49 + 57 + 65 + 73 + 81 = 451

a: 29+131+237+763

=160+1000

=1160

b: 65+327+15+73

=65+15+327+73

=80+400

=480

c: \(12+54:8-8\)

=12+3-8

=15-8

=7

d: \(45\cdot58+45\cdot42\)

\(=45\cdot\left(58+42\right)\)

\(=45\cdot100=4500\)

e: \(35\cdot34+35\cdot26+40\cdot35\)

\(=35\cdot\left(34+26+40\right)\)

\(=35\cdot100=3500\)

f: \(65\cdot25+65\cdot45+30\cdot65\)

\(=65\cdot\left(25+45+30\right)\)

\(=65\cdot100=6500\)

g: \(750:\left\lbrace32-\left\lbrack2^2+\left(5\cdot3^2-42\right)\right\rbrack\right\rbrace+100\)

\(=\frac{750}{32-\left\lbrack4+5\cdot9-42\right\rbrack}+100=\frac{750}{32-4-45+42}+100\)

\(=\frac{750}{28-3}+100\)

=750:25+100

=30+100

=130

h: \(\left\lbrace630:\left\lbrack16+3\cdot\left(6+3\cdot4\right)\right\rbrack\right\rbrace-1\)

\(=\frac{630}{16+3\cdot\left(6+12\right)}-1=\frac{630}{16+3\cdot18}-1\)

\(=\frac{630}{70}-1\)

=9-1=8

i: \(5871:\left\lbrack928-\left(247-82\right)\cdot5\right\rbrack+2175^0\)

\(=\frac{5871}{928-165\cdot5}+1\)

\(=\frac{5871}{928-825}+1=\frac{5871}{103}+1=57+1=58\)

k: \(375:\left\lbrace32-\left\lbrack4+\left(5\cdot3^2-42\right)\right\rbrack\right\rbrace-14\)

\(=\frac{375}{32-\left\lbrack4+5\cdot9-42\right\rbrack}-14\)

\(=\frac{375}{32-\left\lbrack4+45-42\right\rbrack}-14=\frac{375}{32-\left(4+3\right)}-14=\frac{375}{32-7}-14\)

\(=\frac{375}{25}-14\)

=15-14

=1

a: =(34-34)+(100-100)=0

b: =-3000-2000=-5000

a.12

b.-62

c.-38

d.14

e.28

a ) l - 8 - 17 l - l - 13 l 

= l - 25 l + 13

= 25 + 13

= 38

b) ( 23 - 49 ) + ( 13 - 49 )

= - 26 + ( - 36 )

= - 62

1: =-12

2: =11