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

Toán Lớp 9: tìm x biết √4x+20 – 2√x+5 + √9x+45 =6

Toán Lớp 9: tìm x biết
√4x+20 – 2√x+5 + √9x+45 =6

Comments ( 2 )

  1. \sqrt{4x+20}-2\sqrt{x+5}+\sqrt{9x+45}=6(x>=-5)
    <=>2\sqrt{x+5}-2\sqrt{x+5}+3\sqrt{x+5}=6
    <=>3\sqrt{x+5}=6
    <=>\sqrt{x+5}=2
    <=>x+5=4
    <=>x=-1(tm)
    Vậy S={-1}
     

  2. Lời giải và giải thích chi tiết:
    ĐKXĐ : x>=-5
    sqrt(4x+20)-2sqrt(x+5)+sqrt(9x+45)=6
    <=> sqrt(4(x+5))-2sqrt(x+5)+sqrt(9(x+5))=6
    <=> 2sqrt(x+5)-2sqrt(x+5)+3sqrt(x+5)=6
    <=> 3sqrt(x+5)=6
    <=> sqrt(x+5)=2
    <=> x+5=4
    <=> x=-1 \ \ text{(tmđk)}
    Vậy S={-1}

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

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