\(a,5\cdot5\cdot5\cdot5=5^4\\b,9\cdot9\cdot9\cdot9\cdot9\cdot9\cdot9=9^7\\c,7\cdot7\cdot7\cdot7\cdot7=7^5\\d,a\cdot a\cdot a\cdot a\cdot a\cdot a\cdot a\cdot a=a^8\)

a/ 5⁴

b/9⁷

c/7⁵

d/a⁸

\(a\))\(5.5.5.5=5^4\) 

\(b\))\(9.9.9.9.9.9.9=9^7\) 

\(c\))\(7.7.7.7.7=7^5\)

\(d\))\(a.a.a.a.a.a.a.a=a^8\)

\(\begin{array}{l}{3^3}{.3^4} = {3^{3 + 4}} = {3^7};\\{10^4}{.10^3}  = 10^{4+3}= {10^7};\\{x^2}.{x^5} = x^{2+5} = {x^7}.\end{array}\

1.
a) \(3^4\times3^5\times3^6=3^{4+5+6}=3^{15}\)

b) \(5^2\times5^4\times5^5\times25=5^2\times5^4\times5^5\times5^2=5^{2+4+5+2}=5^{13}\)

c) \(10^8\div10^3=10^{8-3}=10^5\)

d) \(a^7\div a^2=a^{7-2}=a^5\)

2.

\(987=900+80+7\\ =9\times100+8\times10+7\\ =9\times10^2+8\times10^1+7\times10^0\)

\(2021=2000+20+1\\ =2\times1000+2\times10+1\times1\\ =2\times10^3+2\times10^1+1\times10^0\)

\(abcde=a\times10000+b\times1000+c\times100+d\times10+e\times1\\ =a\times10^4+b\times10^3+c\times10^2+d\times10^1+e\times10^0\)

còn bài 2

a)  a b c =   a . 100   +   b . 100   +   c . 1   =   a . 10 2   + b .   10 1 +   c . 10 0

b)  a b c d ¯ =   a . 1000   +   b . 100   +   c . 10   +   d   =   a . 10 3   +   b . 10 2   +   c . 10 1   +   d . 10 0

a)  538 = 5 . 100 + 3 . 10 + 8 . 1 = 5 . 10 2 + 3 . 10 1 + 8 . 10 0 .

b)  8609 = 8 . 1000 + 6 . 100 + 9 . 1 = 8 . 10 3 + 6 . 10 2 + 9 . 10 0 .

a)  a . 10 2 + b . 10 0

b)  a . 10 3 + b . 10 1 + c . 10 0

a)  1 . 10 2 + 2 . 10 1 + 6 . 10 0

b)  1 . 10 4 + 6 . 10 2 + 8 . 10 0

\(1024=2^{10}\)

a) 7.7.7.7.7 = 7⁵

b) 12.12….12 = 12ⁿ ( n thừa số 12)