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

Toán Lớp 8: Tìm x : 1) (x – 2)(x² + 2x + 5) + 2(x – 2)(x + 2) – 5(x – 2) =0

Tháng Bảy 23, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Tìm x :
1) (x – 2)(x² + 2x + 5) + 2(x – 2)(x + 2) – 5(x – 2) =0

Comments ( 2 )

  1. dananhthumai
    dananhthumai
    23 Tháng Bảy, 2022 at 6:37 sáng
    Reply
    1) (x-2) (x^2+2x+5) + 2 (x-2) (x+2) – 5 (x-2) = 0
    ⇔ x^3 + x – 10 + 2 (x^2-4) – 5x + 10 = 0
    ⇔ x^3 – 4x + 2x^2 – 8 = 0
    ⇔ x^2 (x+2) – 4 (x+2) = 0
    ⇔ (x^2-4) (x+2) = 0
    ⇔ (x-2) (x+2) (x+2) = (x-2) (x+2)^2
    +) x – 2 = 0
    ⇔ x = 2
    +) (x+2)^2 = 0
    ⇔ x + 2 = 0
    ⇔ x = -2
    $\text{Vậy …. }$
     

  2. danvanthu
    danvanthu
    23 Tháng Bảy, 2022 at 6:37 sáng
    Reply
    ~ Bạn tham khảo ~
    (x – 2)(x² + 2x + 5) + 2(x – 2)(x + 2) – 5(x – 2) =0
    <=> x^3 + 2x^2 + 5x – 2x^2 – 4x – 10 + 2x^2 – 8 – 5x+10=0
    <=> x^3 + 2x^2 -4x – 8 =0
    <=> x^2(x+2) – 4(x+2)=0
    <=> (x+2)(x^2-4)=0
    <=>(x+2)(x+2)(x-2)=0
    <=>(x-2)(x+2)^2=0
    <=> [(x-2=0),(x+2=0):}
    <=> [(x=2),(x=-2):}
    Vậy S={+-2}

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

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