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

Toán Lớp 8: Tìm `x`, biết: `x(3x+2)+(x+1)^2-(2x-5)(2x+5)=0

Toán Lớp 8: Tìm x, biết:
x(3x+2)+(x+1)^2-(2x-5)(2x+5)=0

Comments ( 2 )

  1. x(3x+2)+(x+1)^2-(2x-5)(2x+5)=0
    <=>(3x^2+2x)+(x^2+2x+1)-(4x^2-25)=0
    <=>3x^2+2x+x^2+2x+1-4x^2+25=0
    <=>(3x^2+x^2-4x^2)+(2x+2x)+(1+25)=0
    <=>4x+26=0
    <=>4x=-26
    <=>x=-13/2
    Vậy x=-13/2

  2. x(3x+2) + (x+1)^2 – (2x-5)(2x+5) = 0
    <=> 3x^2 + 2x + x^2 + 2x + 1 – 4x^2 + 25 = 0
    <=> (3x^2 + x^2 – 4x^2) + (2x + 2x) + (1+25) = 0
    <=> 4x + 26 = 0
    <=> 4x = -26
    <=> x = -13/2
    Vậy x = -13/2

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