`485-6(2x-10)=5`

`6(2x-10)=485-5=480`

`2x-10=480:6=80`

`2x=80+10=90`

`x=90:2=45`

\(485-6\left(2x-10\right)=5\\ 6\left(2x-10\right)=480\\ 2x-10=80\\ 2x=90\\ x=45\)

1) Ta có: \(A=1+2+2^2+2^3+...+2^{11}\)

\(=\left(1+2+2^2\right)+\left(2^3+2^4+2^5\right)+...+\left(2^9+2^{10}+2^{11}\right)\)

\(=7+2^3\left(1+2+2^2\right)+...+2^9\left(1+2+2^2\right)\)

\(=7+2^3.7+...+2^9.7\)

\(=7\left(1+2^3+...+2^9\right)\)

Ta thấy \(7⋮7\Rightarrow7\left(1+2^3+...+2^9\right)⋮7\)

\(\Rightarrow A⋮7\)

485-6( 2x-10)= 5

= 6( 2x-10) = 485 - 5

= 6( 2x-10) = 480

= ( 2x-10)  = 480:6

=  2x-10 = 80

= 2x =  80+10

= 2 x=  90

= x = 90: 2

= x = 45

`485-6.(2x-10)=5`

`6.(2x-10)=485-5`

`6.(2x-10)=480`

`2x-10=480:6`

`2x-10=90`

`2x=90+10`

`2x=100`

`x=100:2`

`x=50`

Vậy `x=50`

`#LeMichael`

a, 25.5.4.31.2

= (25.4)(5.2).31

=100.10.31

=31000

b, 37.64 + 37.36

= 37.(64 + 36)

= 37 . 100

= 3700

c, 98.31 + 62

= 98.31 + 31 .2

= 31.( 98 + 2)

= 31 . 100

= 3100

d, 625 . 2 = 1250

e, 375 .4  = 15.25 .4 = 15.100= 1500

g, (1+3+5+7+....+2001) . (135.135.137.- 135.137.137)

= (1+3+5+7+....+2001).(1001.135.137 - 135.137.1001)

= (1+3+5+7+....+2001).0

= 0

giải giúp mik 

giải giúp mik với mn 

`24 xx ( 15 + 49) + 12 xx (50 + 42)`

`=24 xx 64 + 12 xx 92`

`=24 xx 64 + (12 xx2) xx 46`

`= 24 xx 64 + 24 xx 46`

`= 24 xx ( 64 + 46)`

`=24 xx 110`

`=24 xx 100 + 24 xx 10`

`=2400 + 24 xx 10`

`=2400 + 240`

`=2640`

`#LeMichael`

24.(15+49)+12(50+42)

=24.64+12.92

=24.64+24.46

=24.110=2640

`891 + (359 + 190)`

`=891 + 359 + 190`

`=(891 + 359) + 190`

`=1250 + 190`

`=1440`

  891 +( 359 + 190 )

= 891 + 359 + 190

= 1250 + 190

= 1440