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   21*7^2 -11*7^2 +90*7^2 +49*125*16

=7^2* ( 21 -11+ 90 ) + 7^2* 2000

=7^2* 100 + 7^2* 2000

=7^2* ( 100+ 2000 )

=49*2100

=102900

đáp số là 41650

\( 21 . 7^2 - 11 . 7^2 + 90 . 7^2 + 49 . 125 . 16\)

\(=21.7^2-11.7^2+90.7^2+7^2(125.8).2\)

\(=7^2(21-11+90+2000)\)

\(=49.2100=102900\)

a, ( - 5 ) . ( - 7 ) . 4 . 20 . ( - 25 )

= -70000

 b, ( - 16 ) . 73 + ( - 16 ) . 27

= -1600

c, ( - 48 ) . 159 - ( - 48 ) . 59

= -4800

d , 72 . ( - 83 ) + ( - 72 ) . ( - 125 )

= 3014

e , ( - 81 ) . 125 - 181 . ( - 125 )

= 12500

#Hoctot

a -70000.0000 

b-1600.000000

c-4800.000000

d-4968.000000

e-12500.00000

a, 70000

b, 1600

c, 4800

d, 3014

e, 12500

1: Ta có: \(2155-\left(174+2155\right)+\left(-68+174\right)\)

\(=2155-174-2155-68+174\)

=-68

2) Ta có: \(-25\cdot72+25\cdot21-49\cdot25\)

\(=-25\cdot\left(72-21+49\right)\)

\(=-25\cdot100=-2500\)

a, \(35\times34+35\times86+65\times75+65\times45\)

\(=35\times(34+86)+65\times(75+45)\)

\(=35\times120+65\times120\)

\(=(35+65)\times120=100\times120=12000\)

b, \(21\times7^2-11\times7^2+90\times7^2+49\times125\times16\)

Làm nốt

a)35 x 34 + 35x 86 + 65 x 75 + 65 x 45

=35 x (34+86) + 65 x (75 + 45)

=35 x 120 + 65 x 120

=120 x (35 + 65)

=120 x 100

=12000

Chúc học tốt!

b) 21 x 7² - 11 x  7² + 90 x 7² + 49 x  125 x 16

=7² x (21-11+90) + 49  x  2000

=49 x 100 + 49 x 20 x 100

=49 x 100 x (1+20)

=4900 x 21

=102900

Chúc học tốt!