Toán Lớp 6: tìm x biết
b > $3^{x}$ + 2 x $3^{x – 1}$ + $3^{x + 1}$ = 42
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Toán Lớp 6: tìm x biết
b > $3^{x}$ + 2 x $3^{x – 1}$ + $3^{x + 1}$ = 42
Comments ( 2 )
3^(x-1).3+2.3^(x-1)+3^(x-1).9=42
3^(x-1).(3+2+9)=42
3^(x-1).14=42
3^(x-1)=42:14
3^(x-1)=3
3^(x-1)=3^1
=>x-1=1
=>x=1+1
=>x=2
Vậy x=2