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

Toán Lớp 8: A,3(x-1)/4 +1>x+2/3 B,x-2/x+2-3/x-2=2(x-11)/x^2-4

Tháng Mười Hai 11, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: A,3(x-1)/4 +1>x+2/3
B,x-2/x+2-3/x-2=2(x-11)/x^2-4

Comments ( 2 )

  1. quynhthanhnhu
    quynhthanhnhu
    11 Tháng Mười Hai, 2022 at 1:20 chiều
    Reply
    a) (3(x-1))/4+1>(x+2)/3
    <=> (3(x-1)+4)/4-(x+2)/3>0
    <=> (3(3x-3+4)-4(x+2))/12>0
    => 9x+3-4x-8>0
    <=> 5x-5>0
    <=> 5x>5
    <=> x>1
    Vậy x>1
    b) (x-2)/(x+2)-3/(x-2)=(2(x-11))/(x^2-4) ĐK: x\ne+-2
    <=> ((x-2)^2-3(x+2))/(x^2-4)=(2x-22)/(x^2-4)
    => x^2-4x+4-3x-6=2x-22
    <=> x^2-7x-2-2x+22=0
    <=> x^2-9x+20=0
    <=> x^2-5x-4x+20=0
    <=> (x-5)(x-4)=0
    <=> [(x-5=0),(x-4=0):}
    <=> [(x=5),(x=4):} (\text{tm})
    Vậy S={5;4}
     

  2. haiyemy
    haiyemy
    11 Tháng Mười Hai, 2022 at 1:20 chiều
    Reply
    a)
    (3(x-1))/4+1>(x+2)/3
    <=> (9(x-1)+12)/12>(4(x+2))/12
    <=> 9(x-1)+12>4x+8
    <=> 9x-9+12>4x+8
    <=> 9x-4x>8-12+9
    <=> 5x>5
    <=> x>1
    Vậy S={x|x>1}
    b) ĐKXĐ : x ne +-2
    (x-2)/(x+2)-3/(x-2)=(2(x-11))/(x^2-4)
    <=> ((x-2)^2-3(x+2))/(x^2-4)=(2x-22)/(x^2-4)
    => (x-2)^2-3(x+2)=2x-22
    <=> x^2-4x+4-3x-6=2x-22
    <=> x^2-7x-2x+4-6+22=0
    <=> x^2-9x+20=0
    <=> x^2-4x-5x+20=0
    <=> x(x-4)-5(x-4)=0
    <=> (x-5)(x-4)=0
    <=> [(x=5 \ \ \text{(tm)}),(x=4 \ \ \text{(tm)}):}
    Vậy S={4;5}

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

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