100.2²
=100² +2×100×0.2+0.2²
=10000+40+0.04
=10400.004
98×98
=（100-2）²
=100² -2×100×2+2²
=10000-400+4
=9604
37²
=（40-3）²
=40² -2×40×3+3²
=1600-240+9
=1369
（20又2/1）²
=20² +2×20×1/2+1/2²
=400+20+1/4
=420又1/4
2008²
=2000² +2×2000×8+8²
=4000000+32000+64
=4032064
（14又3/4)²
=15² -2×15×1/4+1/4²
=225-15/4+1/16
=221又5/16