a, \(108^2-92^2=\left(108-92\right)\left(108+92\right)=16.200=3200\)

c, \(31^2-31.22+11^2=31^2-2.31.11+11^2=\left(31-11\right)^2=20^2=400\)

a: \(108^2-92^2=3200\)

b: \(102^2+128\cdot26-27^2=9675+3328=13003\)

c: \(31^2-31\cdot22+11^2=20^2=400\)

a: \(73^2-27^2=\left(73-27\right)\left(73+27\right)=100\cdot46=4600\)

b: \(37^2-17^2=\left(37-17\right)\left(37+17\right)=20\cdot54=1080\)

c: \(2002^2-2^2=\left(2002-2\right)\left(2002+2\right)=2004\cdot2000=4008000\)

a) 73² - 27²

= ( 73 + 27 ) ( 73 - 27 )

= 100 . 46

= 4600

b) 37² - 13²

= ( 37 + 13 ) ( 37 - 13 )

= 50 . 24 

= 1200

c) 2002² - 2²

= ( 2002 + 2 ) ( 2002 - 2 )

= 2004 . 2000

= 4008000

a)

=25 . 13 . 4. (-1) = 100.(-13)=-1300

b)

= -79.73 + 79.27 + 73. 79 - 73. 27

=79. 27 - 73. 27

=27. 6=162

1. Phuc will look through a new English book tomorrow.

2. Which ethnic group has the largest population in Vietnam?

a) 73² - 27²
= (73 - 27)(73 + 27)
= 46 . 100
= 4600

b) 37² - 13²
= (37 - 13)(37 + 13)
= 24 . 50
= 1200

c) 2002² - 2²
= (2002 - 2)(2002 + 2)
= 2000 . 2004
= 4008000

a ) 73² - 27² = 43²

b ) 37² - 13² = 24²

c ) 2002² - 2² = 1998²

Bài giải:

a) 73² – 27² = (73 + 27)(73 – 27) = 100 . 46 = 4600

b) 37² - 13² = (37 + 13)(37 – 13) = 50 . 25 = 100 . 12 = 1200

c) 2002² – 2² = (2002 + 2)(2002 – 2) = 2004 . 2000 = 400800

73^2-27^2=(73-27)(73+27)=46.100=4600

a)\(69^2-31^2=\left(69-31\right)\left(69+31\right)=38.100=3800\)

\(1023^2-23^2=\left(1023-23\right)\left(1023+23\right)=1000.1046=1046000\)

\(c,\left(27+73\right)^2-2.27.73+54.73\)

\(100^2-54.73+54.73=10000\)

\(d,\left(63-13\right)^2+2.13.63-26.63=50^2=2500\)