Tính nhanh: a, 21² b, 62.58 c, 119² d, 99² e, 499² f, 299.301 g, 81² h, 102² 16/07/2021 Bởi Eva Tính nhanh: a, 21² b, 62.58 c, 119² d, 99² e, 499² f, 299.301 g, 81² h, 102²
a)21² =(20+1)² =20²+2.20.1+1² =400+40+1 =441 b)62.58 =58.62 =(60-2)(60+2) =60²-2² =3600-4 =3596 c)119² =(120-1)² =120²-1² =14400-1 =14399 d)99² =(100-1)² =100²-2.100.1+1² =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 =80²+2.80.1+1² =6400+160+1 =6561 h)102² =(100+2)² =100²+2.100.2+2² =10000+400+4 =10404 Chúc bạn học tốt Bình luận
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 Bình luận
a)21²
=(20+1)²
=20²+2.20.1+1²
=400+40+1
=441
b)62.58
=58.62
=(60-2)(60+2)
=60²-2²
=3600-4
=3596
c)119²
=(120-1)²
=120²-1²
=14400-1
=14399
d)99²
=(100-1)²
=100²-2.100.1+1²
=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
=80²+2.80.1+1²
=6400+160+1
=6561
h)102²
=(100+2)²
=100²+2.100.2+2²
=10000+400+4
=10404
Chúc bạn học tốt
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