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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: 4 * 8^x – 2 * 3^x – 16 = 0 p/s bốn nhân tám mũ x trừ 2 nhân 3 mũ x trừ 16 bằng 0

Toán Lớp 7: 4 * 8^x – 2 * 3^x – 16 = 0
p/s bốn nhân tám mũ x trừ 2 nhân 3 mũ x trừ 16 bằng 0

Comments ( 2 )

  1. ĐỀ: 4* 8^x – 2 * 2^(3x) – 16 = 0
    ⇒ 4* 8^x – 2 * (2^3)^x – 16 = 0
    ⇒ 4* 8^x – 2 * 8^x – 16 = 0
    ⇒ 2 * 8^x *(2-1) – 16 = 0
    ⇒ 2 * 8^x *1 – 16 = 0
    ⇒ 2 * 8^x – 16 = 0
    ⇒ 2 *( 8^x – 8 ) = 0
    ⇒ 8^x – 8 = 0
    ⇒ 8^x = 8
    ⇒ x  = 1

  2. Sửa đề: 4.8^x-2.3^x-16=0
    ->4.8^x-2.2^(3x)-16=0
    ________________________
    4.8^x-2.2^(3x)-16=0
    ↔2^2 .(2^3)^x-2.2^(3x)-2^4=0
    ↔2^2 .2^(3x)-2.2^(3x)-2^4=0
    ↔2^(3x).(2^2-2)-2^4=0
    ↔2^(3x).2-2^4=0
    ↔2^(3x+1)-2^4=0
    ↔2^(3x+1)=2^4
    ↔3x+1=4
    ↔3x=3
    ↔x=1
    Vậy x=1

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222-9+11+12:2*14+14 = ? ( )