Câu a:

5.2\(^2\) + x + 3 = 5\(^2\)

5.4 + x +3 = 25

20 + x + 3 = 25

x = 25- 20 - 3

x = 5 - 3

x = 2

Vậy x = 2

Câu b:

2\(^3\) + x - 3\(^2\) = 5\(^3\) - 4\(^3\)

8 + x - 9 = 125 - 64

x = 125 - 64 + 9 - 8

x = 61 + 9 - 8

x = 70 - 8

x = 62

Vậy x = 62

1m³ = 1000dm³

209m³ = 209000 dm³

34,6m³ = 34600 dm³

2/5m³ = 400 dm³

Tk mk nha

1 m³ = 1000 dm³

209 m³ = 209000 dm³

34,6 m³ = 34600 dm³

\(\frac{2}{5}\)m³ = 400dm³

a,6840 kg=6,48 tấn

b, 5 m³190³=5,119 m³

c,2 1/4 ngày=54 giờ

d,300 cm³ 4 mm³=300004 mm³

a. 6,84

b. 5,19

c. 54

d. 300004

a)=0,018

b)=0,216

c)1,05

d)=6000 (tick nha

a)180cm²=0,018m²

b)216000cm³=0,216m³

c)105dm²=1,05m²

d)6dm³=6000cm³

\(5m25cm=525cm\)

\(5m^26dm^2=506dm^2\)

\(66m^266cm^2=660066cm^2\)

\(\frac{3}{5}ha+\frac{2}{7}ha=\frac{31}{35}ha\)

\(\frac{2}{7}m^2:2+6m^2=\frac{43}{7}m^2\)

5^6+5^7+5^8

=5^6.(1+5+5^2)

=5^6.31 chia hết cho 31

7^6+7^5-7^4

=7^4.(7^2+7-1)

=7^4.55 chia hết cho 11

BÀI 2:

a)  \(5^6+5^7+5^8=5^6\left(1+5+5^2\right)=5^6.31\)      \(⋮\)\(31\)

b)  \(7^6+7^5-7^4=7^4.\left(7^2+7-1\right)=7^4.55\)\(⋮\)\(11\)

c)  \(2^3+2^4+2^5=2^3.\left(1+2+2^2\right)=2^3.7\)\(⋮\)\(7\)

d) mk chỉnh đề

 \(1+2+2^2+2^3+...+2^{59}\)

\(=\left(1+2\right)+\left(2^2+2^3\right)+...+\left(2^{58}+2^{59}\right)\)

\(=\left(1+2\right)+2^2\left(1+2\right)+...+2^{58}\left(1+2\right)\)

\(=\left(1+2\right)\left(1+2^2+...+2^{58}\right)\)

\(=3\left(1+2^2+...+2^{58}\right)\)\(⋮\)\(3\)

3km45m=3045m=3,045km

4km9m=4009m=4,009km

112dm=11,2m

256cm=2,56m

\(3km45m=3,045km\)

\(4km9m=4,009km\)

\(112dm=11,2m\)

\(256cm=2,56m\)

\(1,2km^2=120ha\)

\(3,65m^2=365dm^2\)

\(750000m^2=75ha\)

\(200000cm^2=20m^2\)

56000m³= 56 dam³ 

12,56 cm²=1256 mm²         1mm=0,001m

12cm²=0,0012 m²               982662cm³= 982,662m³

1km³= 1000000000000000000mm³               1m³= 1 000 000 000 mm³

mình nhầm nhé 1mm=.........1m