Toán Lớp 6: Tìm x, biết :
a, 5 mũ x . 25=125
b, 243:3 mũ x=27
c, 2 mũ x+2=64
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Toán Lớp 6: Tìm x, biết :
a, 5 mũ x . 25=125
b, 243:3 mũ x=27
c, 2 mũ x+2=64
Comments ( 2 )
5^x . 25=125
=>5^x . 5^2=5^3
=>5^x =5^3:5^2
=>5^x=5^(3-2)
=>5^x=5^1
=>x=1
Vậy x=1
b)
243:3^x=27
=>3^5:3^x=3^3
=>3^x=3^5:3^3
=>3^x=3^2
=>x=2
Vậy x=2
c)
2^(x+2)=64
=>2^(x+2)=2^6
=>x+2=6
=>x=6-2
=>x=4
Vậy x=4