1. Tính bằng cách hợp lí.

Nhận xét: (100-1)x(100-2)x(100-3)x.... ( có 100 thừa số)

Tức là sẽ có thừa số 100-100=0

Nghĩa là: (100-1)x(100-2)x(100-3)x...x(100-100)=(100-1)x(100-2)x(100-3)x...x0=0

2. 

1224:[ 115-(5+2x4)]=1224:[115-(5+8)]=1224:[115-13]=1224:102=12

Vì tích trên có 100 thừa số nên 

=>n=100

=(100-1)(100-2)(100-3)...(100-100)

=0

vậy 

1224:[115-(5+2x4)]

=1224:[115-(5+8)]

=1224:[115-13]

=1224:102

=12

hc tốt

a) 115 + 5 ( x – 4 ) = 120

5 ( x – 4 ) = 120 – 115

5 ( x – 4 ) = 5

x – 4 = 5 : 5

x – 4 = 1

x = 1 + 4

x = 5

b)  5|x| –  10 0 = 3 7 : 3 5

5| x | – 1 =  3 2

5| x | = 9 + 1

5| x | = 10

| x | = 2

x = 2 hoặc x = -2

c)  2 2016 . 2 x - 1 = 2 2015

2 x - 1 = 2 2015 :   2 2016

2 x - 1 = 2 2015 - 2016

2 x - 1 = 2 - 1

⇒ x – 1 = -1

x = -1 + 1

x = 0

câu 1

ko ghi lại đề

=6x6-6x3

=36-18

=18

tính nhanh nha các bạn

\(90:15\times6-6\times3\)

\(=6\times6-6\times3\)

\(=6\times\left(6-3\right)\)

\(=6\times3=18\)

~ Hok tốt ~

a) = 8 . 15 - [115- 7² ]

     = 8 . 15 - [115- 49 ]

     = 120    - 56

      = 64

b) = 100 : {250 : [450 - (2.125 - 8.25)]}

    = 100 : {250 : [450 - (250 - 200 )]}

     = 100 : {250 : [450 - 50]}

     = 100 : {250 :400}

     = 100 : 0,265

      = 0,00265

     = 

\(a,2^3.15-\left[115-\left(12-5\right)^2\right]\)

\(=8.15-\left[115-\left(12-5\right)^2\right]\)

\(=120-\left[115-7^2\right]\)

\(=120-\left[115-49\right]\)

\(=120-66\)

\(=54\)

\(b,100:\left\{250:\left[450-\left(2.5^3-2^3.25\right)\right]\right\}\)

\(=100:\left\{250:\left[450-\left(2.125-8.25\right)\right]\right\}\)

\(=100:\left\{250:\left[450-\left(250-200\right)\right]\right\}\)

\(=100:\left\{250:\left[450-50\right]\right\}\)

\(=100:\left\{250:400\right\}\)

\(=100:0,625\)

\(=160\)

a: \(2^3\cdot15-\left[115-\left(12-5\right)^2\right]\)

\(=8\cdot15-115+7^2\)

\(=54\)

b: \(100:\left\{250:\left[450-\left(2\cdot5^3-2^3\cdot25\right)\right]\right\}\)

\(=100:\left\{250:\left[450-50\right]\right\}\)

\(=100:\left\{250:400\right\}\)

\(=100:\dfrac{5}{8}=160\)

Mik làm 1 câu thôi sức ko

\(2^3.15-\left[115-\left(12-5\right)^2\right]=8.15-\left[115-7^2\right]=120-\left[115-49\right]=120-66=54\)

\(100:\left\{250:\left[450-\left(4.5^3-2^2.25\right)\right]\right\}=100:\left\{250:\left[450-\left(4.125-4.25\right)\right]\right\}=100:\left\{250:\left[450-\left(500-100\right)\right]\right\}\)

\(=100:\left[250:\left(450-400\right)\right]=100:\left(250:50\right)=100:5=20\)

a,2³ . 15 -[115-\((\)12-5)²]

= 8. 15 - [115- 7² ]

=120-[115-49]

=120-66

=54

b, 100:{250:[450-\((\)4.5³ - 2³.25)]}

=100:{250:[450-\((\)4.125-8.25)]}

=100:{250:[450-\((\)500-300)]}

=100:{250:[450-200]}

=100:{250:250}

=100:1

=100

\(\dfrac{15}{100}=0,15\)

\(115\%=\dfrac{115}{100}=1,15\)

Mà \(0,15< 1,15\)

Vậy \(\dfrac{15}{100}< 115\%\)

____________

\(\dfrac{5}{2}=2,5\)

Vậy \(\dfrac{5}{2}=2,5\)

a:<

b: =

\(\dfrac{15}{100} = 115% \)%

\(\dfrac{5}{2}=2,5\)

10x3^3(x-2)=(3¹¹⁷+3¹¹⁵):3¹⁰⁰

10x3^3(x-2)=3¹¹⁷:3¹⁰⁰+3¹¹⁵:3¹⁰⁰

10x3^3(x-2)=3^117-100+3^115-100

10x3^3(x-2)=3¹⁷+3¹⁵

10x3^3(x-2)=129 140 163+14 348 907

10x3^3(x-2)=143 489 070

3^3(x-2)=143 489 070:10

3^3(x-2)=14 348 907

3^3(x-2)=3¹⁵

=>3(x-2)=15

x-2=15:3

x-2=5

x=5+2

x=7

10.3^{3 . (x-2)}= (3¹¹⁷ + 3¹¹⁵) : 3¹⁰⁰

x=7