\(=56+710+142\\ =908\)

\(=56+142\cdot6=908\)

= 6060

4 x 18 x 25 + (142 x 12 + 142 x 18)

= (4 x 25) x 18 + (142 x (12 + 18))

= 100 x 18 + (142 x 30)

= 1800 + 4260

= 6060

4*18*25+(142*12+142*18)=

4×25×18+[142×(12+18)]

=100×18+[142×30]

=1800+4260

=6060

\(\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+...+\dfrac{1}{142}-\dfrac{1}{144}\right)\)

\(=\dfrac{5}{2}\left(\dfrac{1}{2}-\dfrac{1}{144}\right)=\dfrac{355}{288}\)

a) 142 x 12 + 142 x 18

= 142 x ( 18 + 12 )

= 142 x 30

= 4260

b) 49 . 365 - 39 . 365

= 365 . ( 49 - 39)

= 365 . 10

= 3650

c) 4 . 18 . 25

= 18 . 4 . 25

= 18 . 100

= 1800

a, 142 x 12 + 142 x18=142 x (12+18)= 4260

b, 49 x 365 - 39 x356 = 356 x (49-39)= 3560

c,4 x 18 x 25 = (25 x 4) x 18=1800

a,142 x 12 + 142 x 18 

=142 x (12+18)

=4260

b,49 x 365 - 39 x 365

= 365 x ( 49 -39 )

=365 x 10

=3650

c,4 x 18 x 25

=(4 x 25 ) x 18

= 100 x 18

= 1800

Bài 2: Tính bằng cách thuận tiện nhất

\(\text{a. 1255 + 436 + 145}\)

\(=\left(1255+145\right)+436\)

\(=1400+436\)

\(=1836\)

\(\text{b. 142 x 12 + 142 x 18}\)

\(=142\times\left(12+18\right)\)

\(=142\times30\)

\(=4260\)

\(\text{c. 4 x 18 x 25}\)

\(=\left(25\times4\right)\times18\)

\(=100\times18\)

\(=1800\)

Bài 2:

a: \(=1400+436=1836\)

b: =142(12+18)

=142*30

=4260

c: \(=100\cdot18=1800\)

Bài 3:

a: \(41m^219dm^2>409dm^2\)

b: \(90000cm^2< 90m^2\)

c: \(30m^26dm^2< 3060dm^2\)

d: \(8012cm^2>8dm^212cm^2\)

e: \(5dm^29cm^2=509cm^2\)

f: \(3940dm^2=39m^240dm^2\)

g: \(300m^26dm^2>3006dm^2\)

h: \(2009cm^2< 21dm^2\)

a) c1 : = 142 x 9 + 142 x 1 

= 142 x ( 9 + 1 )

= 142 x 10

= 1420

c2 : = 142 x 9 + 142

= 1278 + 142 

= 1420

Cách 1: 142 x 9 + 124 = 1278 + 124 = 1420
Cách 2: 142 x 9 + 124 = 142 x 9 + 142 x 1 = 142 x ( 9 + 1 ) = 142 x 10 = 1420

2739 

tick cho mình với

142 * 3 + 425 * 5 + 752 / 4 = 426 + 2125 + 188

= 2551 + 188

= 2739

a)  x = 7 8 x = − 3 8

b)  x = 7 8 x = − 3 8