18 mũ 2 bằng bao nhiêu

` 3. `

` a) 3^7 . 27^5 . 81^3 `

` =3^7 . (3^3)^5 . (3^4)^3 `

` =3^7 . 3^{15} . 3^{12} `

` =3^{34} `

` b) 36^5 : 18^5 `

` =(36:18)^5 `

` =2^5=32 `

` c) 24 . 5^5 + 5^2 . 5^3 `

` =24 . 5^5 + 5^5 `

` =5^5 . (24+1) `

` =5^5 . 25 `

` =5^5 .5^2=5^7 `

` d)125^4 : 5^8 `

` =(5^3)^4 : 5^8 `

` =5^{12} : 5^8 `

` =5^4=625 `

` B4. `

` a) 2^x . 4=16 `

` => 2^x = 4=2^2 `

` =>x=2 `

` b)3^x . 3=243 `

` =>3^x=81=3^4 `

` =>x=4 `

` c) 64 . 4^x=16^8 `

` => 4^3 . 4^x =(4^2)^8 `

` => 4^{x+3}=4^{16} `

` =>x+3=16 `

` =>x=13 `

` d)2^x . 16^2=1024 `

` =>2^x . (2^4)^2=2^{10} `

` => 2^x . 2^8=2^{10} `

` => 2^x = 2^{10}:2^8 `

` =>2^x=2^2 `

` =>x=2 `

Giải thích các bước giải:

` a^n =a.a.a....a(n ` thừa số ` a) `

` a^n . b^n=(a.b)^n `

` a^n : b^n=(a:b)^n ``

` (a^n)^m=a^{n.m} `

` a^n . a^m=a^{n+m} `

` a^n : a^m = a^{n-m} `