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

Toán Lớp 8: So sánh: E=(3+1)(3 ²+1)(3^4+1)(3^8+1)(3^16+1) và F=3^32-1

Toán Lớp 8: So sánh:
E=(3+1)(3 ²+1)(3^4+1)(3^8+1)(3^16+1) và F=3^32-1

Comments ( 2 )

  1. $E=(3+1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)$
    $(3-1)E=(3-1)(3+1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)$
    $2E=(3^2-1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)$
    $2E=(3^4-1)(3^4+1)(3^8+1)(3^16+1)$
    $2E=(3^8-1)(3^8+1)(3^16+1)$
    $2E=(3^16-1)(3^16+1)$
    $2E=3^{32}-1$
    $E=\dfrac{3^{32}-1}2$
    Mà $F=3^{32-1} > E=\dfrac{3^{32}-1}2$
    Vầy $F>E$ hay $E<F$

  2. Giải đáp:E<F.
     
    Lời giải và giải thích chi tiết:
    E=(3+1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)
    <=>2E=2.(3+1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)
    <=>2E=(3-1)(3+1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)
    <=>2E=(3^2-1)(3^2+1)(3^4+1)(3^8+1)(3^16+1)
    <=>2E=(3^4-1)(3^4+1)(3^8+1)(3^16+1)
    <=>2E=(3^8-1)(3^8+1)(3^16+1)
    <=>2E=(3^16-1)(3^16+1)
    <=>2E=3^32-1>0
    Mà F=3^32-1
    =>2E=F
    =>E=1/2F<F
    Vậy E<F.

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