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

Toán Lớp 8: Tìm x, biết: a) 6 -2×2+ 2x(x + 1) = 0 b) x(x –3) + 2x -6 = 0

Toán Lớp 8: Tìm x, biết: a) 6 -2×2+ 2x(x + 1) = 0
b) x(x –3) + 2x -6 = 0

Comments ( 2 )

  1. a/ -> 6-4x+2x^2+2x=0
    -> 6-2x+2x^2=0
    -> 3-x+x^2=0
    -> x^2-x+3=0
    x=-(1)±√(-1)²-4.1.3/2.1
    -> 1±√1-12/2
    -> 1±√-11/2
    -> x∉R
    b/ x(x-3)+2(x-3)=0
    -> (x-3)(x+2)=0
    -> x-3=0 hoặc x=-2

  2. a,  ta có  6-2x²+2x(x+1)=0
       => 6-2x²+2x²+2x =0
       =>  6+2x = 0
       =>    2x=-6     =>x=-3
    b,   Ta có  x(x-3)+2x-6 =0 
      =>  x(x-3)+2(x-3) = 0
       =>   (x-3)(x+2) =0 
       =>  x-3=0  hoặc   x+2=0
       =>  x=3 hoặc x=-2 
     

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