Question

1.2005^2-2003^2第二题：51×49第三题：63^2第四题：98^2【用简便方法计算,

Answer 1

2005²-2003²

=(2005+2003)×(2005-2003)

=4008×2

=8016

51×49

=(50+1)×(50-1)

=50²-1²

=2500-1

=2499

63²

=(60+3)²

=60²+2×60×3+3²

=3600+120+9

=3729

98²

=(100-2)²

=100²-2×100×2+2²

=10000-400+4

=9604