Question

tính nhẩm

56.64

75.85

98^2.102^2

 

Answer 1

\(56.64=(60-4)(60+4)=3600-16=3584\)

\(75.85=(80-5)(80+5)=6400-25=6375\)

\(98^2.102^2=(98+102)(98+102)=200,.200=40000\)

Answer 2

`56.64 = (60 -4)(60+4)`

`=60^2 -4^2 = 3600-16`

`=3584`

`75.85`

`=(80-5)(80+5) = 80^2 - 5^2`

`=6400 - 25 = 6375`

`98^2* 102^2`

`= 98 . 102 . 98 .102`

`=(100-2).(100+2) . (100-2).(100+2)`

`= (100^2 - 2^2 ) . (100^2 -2^2)`

`= (10000 -4)^2`

`=9996^2 = 9920016`