a, 21²=(20+1)²=400+40+1=441
b, 62.58=(60+2)(60-2)=3600-4=3596
c, 119²=(120-1)²=14400-240+1=14161
d, 99²=(100-1)²=10000-200+1=9801
e, 499²=(500-1)²=250000-1000+1=249001
f, 299.301=(300-1)(300+1)=90000-1=89999
g, 81²=(80+1)²=6400+160+1=6561
h, 102²=(100+2)²=10000+400+4=10404
XIN TLHN VÀ 5* NHÉ