` 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} `