987=9.100+8.10+7
=9.10 mũ 2+8.10 mũ 1+7.10 mũ 0
2564=2.1000=5.100+6.10+4
=2.10 mũ 3+5.10 mũ 2+6.10 mũ 1+4.10 mũ 0
abcd=a.1000+b.100+c.10+d
=a.10 mũ 3+b.10 mũ 2+c.10 mũ 1+d.10 mũ 0
k cho mk nha
987 = 900 + 80 + 7
= 9 . 100 + 8 . 10 + 7 . 1
= 9 . 102 + 8 . 101 + 7 . 100
2546 = 2000 + 500 + 40 + 6
= 2 . 1000 + 5 . 100 + 4 . 10 + 6 . 1
= 2 . 103 + 5 . 102 + 4 . 101 + 6 . 100
abcd = a . 1000 + b . 100 + c . 10 + d . 1
= a . 103 + b . 102 + c . 101 + d . 100