Toán Lớp 6: tìm x
a,2^X+1 -2^x = 64
b,(3^x -81).(6.x +12)= 0
giúp mik câu này vs minhg cảm ơn
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Toán Lớp 6: tìm x
a,2^X+1 -2^x = 64
b,(3^x -81).(6.x +12)= 0
giúp mik câu này vs minhg cảm ơn
Comments ( 2 )
a)
2^(x+1)-2^x=64
=>2^x . 2-2^x=64
=>2^x . (2-1)=64
=>2^x=64
=>2^x=2^6
=>x=6
Vậy x=6
b)
(3^x-81).(6.x+12)=0
=>[(3^x-81=0),(6.x+12=0):}
=>[(3^x=0+81),(6x=0-12):}
=>[(3^x=81),(6x=-12):}
=>[(3^x=3^4),(x=-12:6):}
=>[(x=4),(x=-2):}
Vậy x\in{-2;4}