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

Toán Lớp 8: 1,Tìm x biết a,3.(x+1)^2+(x-5)^2=4.(x+3).(x-1) b,(2x-1)^2+(x+3)^2-5.(x+7).(x-7)=0 c,(4x-1)^2-3x.(x+3)=-12 d,(3x-2).(9x^2+6x+4)-27x.(x^2

Home/ Toán Lớp 8: 1,Tìm x biết a,3.(x+1)^2+(x-5)^2=4.(x+3).(x-1) b,(2x-1)^2+(x+3)^2-5.(x+7).(x-7)=0 c,(4x-1)^2-3x.(x+3)=-12 d,(3x-2).(9x^2+6x+4)-27x.(x^2

Toán Lớp 8: 1,Tìm x biết a,3.(x+1)^2+(x-5)^2=4.(x+3).(x-1) b,(2x-1)^2+(x+3)^2-5.(x+7).(x-7)=0 c,(4x-1)^2-3x.(x+3)=-12 d,(3x-2).(9x^2+6x+4)-27x.(x^2

Tháng Một 1, 2023 Toán học 2 Comments 0 views

Toán Lớp 8: 1,Tìm x biết
a,3.(x+1)^2+(x-5)^2=4.(x+3).(x-1)
b,(2x-1)^2+(x+3)^2-5.(x+7).(x-7)=0
c,(4x-1)^2-3x.(x+3)=-12
d,(3x-2).(9x^2+6x+4)-27x.(x^2-3)=6
giúp với ạ mình cần gấp

Comments ( 2 )

  1. tuyen98
    tuyen98
    1 Tháng Một, 2023 at 11:15 chiều
    Reply
    a)3(x+1)²+(x-5)²=4(x+3)(x-1)
    ⇔3(x²+2x+1)+x²-10x+25=(4x+12)(x-1)
    ⇔3x²+6x+3+x²-10x+25=4x²-4x+12x-12
    ⇔(3x²+x²)+(6x-10x)+(3+25)=4x²+(-4x+12x)-12
    ⇔4x²-4x+28=4x²+8x-12
    ⇔4x²-4x-4x²-8x=-12-28
    ⇔-12x=-40
    ⇔x=40/12
    ⇔x=10/3
    Vậy x=10/3
    b)(2x-1)²+(x+3)²-5(x+7)(x-7)=0
    ⇔4x²-4x+1+x²+6x+9-5(x²-49)=0
    ⇔4x²-4x+1+x²+6x+9-5x²+245=0
    ⇔(4x²+x²-5x²)+(-4x+6x)+(1+9+245)=0
    ⇔2x+255=0
    ⇔2x=-255
    ⇔x=-255/2
    Vậy x=-255/2
    c)(4x-1)²-3x(x+3)=-12
    ⇔16x²-8x+1-3x²-9x=-12
    ⇔(16x²-3x²)-(8x+9x)+1=-12
    ⇔13x²-17x+1=-12
    ⇔13x²-17x+1+12=0
    ⇔13x²-17x+13=0(vô nghiệm)
    Vậy không có giá trị nào thỏa mãn x
    d)(3x-2)(9x²+6x+4)-27x(x²-3)=6
    ⇔(3x-2)[(3x)²+3x.2+2²]-27x³+81x=6
    ⇔27x³-8-27x³+81x=6
    ⇔(27x³-27x³)+81x-8=6
    ⇔81x-8=6
    ⇔81x=6+8
    ⇔81x=14
    ⇔x=14/81
    Vậy x=14/81

  2. phuongthaongoc
    phuongthaongoc
    1 Tháng Một, 2023 at 11:15 chiều
    Reply
    a)
    3(x+1)^2+(x-5)^2=4(x+3)(x-1)
    \to 3(x^2+2x+1)+(x^2-10x+25)=4(x^2+2x-3)
    \to 3x^2+6x+3+x^2-10x+25=4x^2+8x-12
    \to (3x^2+x^2)+(6x-10x)+(3+25)=4x^2+8x-12
    \to 4x^2-4x+28=4x^2+8x-12
    \to 4x^2-4x^2-4x-8x=-12-28
    \to -12x=-40
    \to x=10/3
    Vậy x=10/3
    b)
    (2x-1)^2+(x+3)^2-5(x+7)(x-7)=0
    \to (4x^2-4x+1)+(x^2+6x+9)-5(x^2-49)=0
    \to 4x^2-4x+1+x^2+6x+9-5x^2+245=0
    \to (4x^2+x^2-5x^2)+(6x-4x)+(1+9+245)=0
    \to 2x+255=0
    \to 2x=-255
    \to x=-255/2
    Vậy x=-255/2
    c)
    (4x-1)^2-3x(x+3)=-12
    \to (16x^2-8x+1)-(3x^2+9x)=-12
    \to 16x^2-8x+1-3x^2-9x+12=0
    \to (16x^2-3x^2)+(-8x-9x)+(1+12)=0
    \to 13x^2-17x+13=0
    mà 13x^2-17x+13\ne0
    Vậy phương trình vô nghiệm
    d)
    (3x-2)(9x^2+6x+4)-27x(x^2-3)=6
    \to (3x)^3-2^3-27x^3+81x=6
    \to 27x^3-8-27x^3+81x=6
    \to 81x-8=6
    \to 81x=14
    \to x=14/81
    Vậy x=14/81

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

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