x+2x+3x+...+1000x=5005x\(10^4\)

ta có:x+2x+3x+...+1000x=x(1+2+3+...+1000)

                                     =x((1000+1):2x1000)

                                     =x500500

\(\Rightarrow\) x500500=5005x\(10^4\) 

x5005.\(100\)=5005x\(10^4\) 

x5005.\(10^2\)=5005x\(10^4\) 

\(\Rightarrow x.10^2=10^4\)

x=\(10^4:10^2\)

x=\(10^2\) 

x=100

\(\left(4+6+8+10+...+2012\right)\cdot\frac{1}{1000}\cdot\left(\frac{1}{2}+\frac{3}{4}+\frac{5}{6}\right)\)

\(\text{Đặt A = 4 + 6 + 8 + 10 + ... + 2012 }\)

SSH của A là : (2012 - 4) : 4 + 1  = 503 (sh) 

Tổng A là : (4 + 2012) . 503 : 2 = 507024 

Thay A vào bt ta đc : \(507024\cdot\frac{1}{1000}\cdot\left(\frac{1}{2}+\frac{3}{4}+\frac{5}{6}\right)\)

\(=507024\cdot\frac{1}{1000}\cdot\frac{25}{12}\)

\(=507024\cdot\frac{1}{480}=\frac{10563}{10}=1056,3\)

10 + 10 + 10 + 10 + 10
= 20 + 10 + 10 + 10
= 30 + 10 + 10
= 40 + 10
= 50
10 + 10 + 10 + 10 + 10
= 10 . 5
= 50
 

90 + 90 + 90 + 90 + 90
= 180 + 90 + 90 + 90
= 270 + 90 + 90
= 360 + 90
= 450
90 + 90 + 90 + 90 + 90
= 90 . 5
= 450
 

10 + 10 + 10 + 10 + 10

= 10 x 5

= 50

90 + 90 + 90 + 90 + 90

= 90 x 5

= 450

10 + 10 + 10 + 10 + 10 = 10 x 5

                                   =50

90 + 90 + 90 + 90 + 90 = 90 x 5

                                   =450

10 x 10 + 90 x 10

= 10 x (90 + 10)

= 10 x      100

=     1000

=100 nha bạn

10x10+90x10

=10x(10+90)

=10x100

=1000

10 + 20 = 50 - x 

30 = 50 - x 

x = 50 - 30

x = 20 

10 + 20 = 50 - x

30 = 50 - x

x = 20

10 + 90 = 10 + x

100 = 10 + x

x = 90

\(10+20=50-x\)

\(30=50-x\)

   \(x=50-30\)

   \(x=20\)

\(10+90=10+x\)

\(100=10+x\)

     \(x=100-10\)

     \(x=90\)

90 + x = 100

        x = 100 - 90

        x = 10

x - 10 = 90

      x = 90 + 10

     x = 100

x - 90 = 10

      x = 10 + 90

      x = 100

k 

90 + x = 100

x = 100 - 90

x = 10

x - 10 = 90

x = 90 + 10

x = 100

x - 90 = 10

x = 10 + 90

x = 100

90 + x = 100

x = 100 - 90

x = 10

x - 10 = 90

x = 10 + 90

x = 100

x - 90 = 10

x = 10 + 90

x = 100

Xong rùi k nhé

a) 927 – 10 x 2 = 927 – 20

                   = 907

b) 163 + 90 : 3 = 163 + 30

                   = 193

c) 90 + 10 x 2 = 90 + 20

                   = 110

d) 106 – 80 : 4 = 106 – 20

                   = 86

a)5+10=30-x

=>15=30-x

=>x=30-15

=>x=15

b)10+40=90-x

=>50=90-x

=>x=90-50

=>x=40

\(5+10=30-x\)

\(15=30-x\)

\(x=15\)

\(10+40=90-x\)

\(50=90-x\)

\(x=40\)

5 + 10 = 30 - x 

15 = 30 - x 

30 - x = 15 ( đổi vế )

x = 30 - 15 

x = 15

10 + 40 = 90 - x 

50 = 90 - x 

90 - x = 50 ( đổi vế )

x = 90 - 50 

x = 40 

nha bn