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

Toán Lớp 8: bai 1 : giai PT a, (x-2) ^2 – (x-3)(x+3) = 6 b, (x+3)^2 + (4+x)(4-x) = 10 c,4(x-3)^2 – (2x-1)(2x+1) =10 d, -4(x-1)^2 + (2x – 1)(2x+1) =

Toán Lớp 8: bai 1 : giai PT
a, (x-2) ^2 – (x-3)(x+3) = 6
b, (x+3)^2 + (4+x)(4-x) = 10
c,4(x-3)^2 – (2x-1)(2x+1) =10
d, -4(x-1)^2 + (2x – 1)(2x+1) = -3

Comments ( 2 )

  1. Giải đáp:
    a)S={7/4}
    b)S={-5/2}
    c)S={9/8}
    d)S={1/4}
    Lời giải và giải thích chi tiết:
    a)(x-2)²-(x-3)(x+3)=6
    ⇔x²-4x+4-(x²-9)=6
    ⇔x²-4x+4-x²+9=6
    ⇔(x²-x²)-4x+(4+9)=6
    ⇔-4x+13=6
    ⇔-4x=6-13
    ⇔-4x=-7
    ⇔x=7/4
    Vậy S={7/4}
    b)(x+3)²+(4+x)(4-x)=10
    ⇔x²+6x+9+16-x²=10
    ⇔(x²-x²)+6x+(9+16)=10
    ⇔6x+25=10
    ⇔6x=10-25
    ⇔6x=-15
    ⇔x=-15/6
    ⇔x=-5/2
    Vậy S={-5/2}
    c)4(x-3)²-(2x-1)(2x+1)=10
    ⇔4(x²-6x+9)-(4x²-1)=10
    ⇔4x²-24x+36-4x²+1=10
    ⇔(4x²-4x²)-24x+(36+1)=10
    ⇔-24x+37=10
    ⇔-24x=10-37
    ⇔-24x=-27
    ⇔x=27/24
    ⇔x=9/8
    Vậy S={9/8}
    d)-4(x-1)²+(2x-1)(2x+1)=-3
    ⇔-4(x²-2x+1)+4x²-1=-3
    ⇔-4x²+8x-4+4x²-1=-3
    ⇔(-4x²+4x²)+8x-(4+1)=-3
    ⇔8x-5=-3
    ⇔8x=-3+5
    ⇔8x=2
    ⇔x=2/8
    ⇔x=1/4
    Vậy S={1/4}

  2. Đáp án:
     
    Giải thích các bước giải:
     

    toan-lop-8-bai-1-giai-pt-a-2-2-3-3-6-b-3-2-4-4-10-c-4-3-2-2-1-2-1-10-d-4-1-2-2-1-2-1

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