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

Toán Lớp 7: `1, (5x^2-7x+3)-(x^2-x+1)=4x` `2, -2(x^3-x^2+x-7)-(x^2-x-1)=-2x^3+x^2-3x+4`

Tháng Một 8, 2023 Toán học 2 Comments 0 views

Toán Lớp 7: 1, (5x^2-7x+3)-(x^2-x+1)=4x
2, -2(x^3-x^2+x-7)-(x^2-x-1)=-2x^3+x^2-3x+4

Comments ( 2 )

  1. diemmyhoa
    diemmyhoa
    8 Tháng Một, 2023 at 3:00 sáng
    Reply
    Giải đáp:
    Azzuri#
    (5x²-7x+3)-(x²-x+1)=4x
    $\Longrightarrow$ 5x²-x²-7x+x-4x+3-1=0
    $\Longrightarrow$4x²-10x+2=0
    $\Longrightarrow$4x²-10x+25/4-17/4=0
    $\Longrightarrow$[(2x)²-2*2x*5/2+(5/2)^2]-17/4=0
    $\Longrightarrow$(2x-5/2)²-17/4=0
    $\Longrightarrow$(2x-5/2-(\sqrt{17})/2)(2x-5/2-(-\sqrt{17})/2)=0
    $\Longrightarrow$
    2x-5/2=(\sqrt{17})/2⇔x=(5+\sqrt{17})/4
    2x-5/2=(-\sqrt{17})/2⇔x=(5-\sqrt{17})/4
    $\Longrightarrow$(5+\sqrt{17})/4;(5-\sqrt{17})/4
    -2x³+2x³+2x²-x²-x²-2x+x+3x-7+1-4=0
    $\Longrightarrow$2x-10=0
    $\Longrightarrow$2x=10
    $\Longrightarrow$x=5
    Lời giải và giải thích chi tiết:
     

  2. lantrungbach
    lantrungbach
    8 Tháng Một, 2023 at 2:59 sáng
    Reply
    #AkaShi
    (5x²-7x+3)-(x²-x+1)=4x
    ⇔5x²-x²-7x+x-4x+3-1=0
    ⇔4x²-10x+2=0
    ⇔4x²-10x+25/4-17/4=0
    ⇔[(2x)²-2*2x*5/2+(5/2)^2]-17/4=0
    ⇔(2x-5/2)²-17/4=0
    ⇔(2x-5/2-(\sqrt{17})/2)(2x-5/2-(-\sqrt{17})/2)=0
    1) 2x-5/2=(\sqrt{17})/2⇔x=(5+\sqrt{17})/4
    1) 2x-5/2=(-\sqrt{17})/2⇔x=(5-\sqrt{17})/4
    Vậy S∈{(5+\sqrt{17})/4;(5-\sqrt{17})/4}
    ………………….
    -2(x³-x²+x-7)-(x²-x-1)=-2x³+x²-3x+4
    ⇔-2x³+2x³+2x²-x²-x²-2x+x+3x-7+1-4=0
    ⇔2x-10=0
    ⇔2x=10
    ⇔x=5
    Vậy x=5

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

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