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

Toán Lớp 10: Câu 1 a)(2x-3)(x+1)-2x(-5)=14 b)(4x^9)-8(2x+3)=0 C)(2x-3)(x+1)-2x(x-15)

Toán Lớp 10: Câu 1
a)(2x-3)(x+1)-2x(-5)=14
b)(4x^9)-8(2x+3)=0
C)(2x-3)(x+1)-2x(x-15)

Comments ( 1 )

  1. Câu 1
    a)(2x-3)(x+1)-2x(-5)=14
    <=> 2x^2+2x-3x-3+10x=14
    <=> 2x^2+9x-17=0
    Tính Δ=9^2 – 4 · 2 · (-17) = 217 > 0
    => pt có 2 nghiệm pb 
    x_1 = $\dfrac{-9+\sqrt{217}}{4}$ 
    x_2 = $\dfrac{-9-\sqrt{217}}{4}$ 
    b)(4x^9)-8(2x+3)=0
    <=> 4x^9 -16x-24=0
    <=> 4(x^9 -4x-6)=0
    <=> x^9 – 4x – 6 =0
    c)(2x-3)(x+1)-2x(x-15)
    <=> 2x^2+2x-3x-3-2x^2+30x=0
    <=> 29x = -3
    <=> x = -3/29

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