Bài 1 : tính nhanh a ) 101 ² b ) 97 . 103 c ) 77 ² + 23 ² + 77. 46 d ) 105 ² – 5 ²

Đáp án:

a,

$101^2=(100+1)^2=100^2+2·100·1+1=10000+200+1=10201$

b,

$97·103=(100-3)(100+3)=100^2-3^2=10000-9=9991$

c,

$77^2+23^2+77·46=77^2+2·77·23+23^2=(77+23)^2=100^2=10000$

d,

$105^2-5^2=(105-5)(105+5)=100·110=11000$