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

Toán Lớp 8: Tìm x biết: a) 6(x+2)(x-3) – 3(x-2)^2 – 3(x-1)(x+1)=1 b) 3(x+2)^2 + (2x-1)^2 – 7(x+3)(x-3)=36 c) (x-1)(x^2 + x + 1) + x(x+2)(2-x) =

Home/ Toán Lớp 8: Tìm x biết: a) 6(x+2)(x-3) – 3(x-2)^2 – 3(x-1)(x+1)=1 b) 3(x+2)^2 + (2x-1)^2 – 7(x+3)(x-3)=36 c) (x-1)(x^2 + x + 1) + x(x+2)(2-x) =

Toán Lớp 8: Tìm x biết: a) 6(x+2)(x-3) – 3(x-2)^2 – 3(x-1)(x+1)=1 b) 3(x+2)^2 + (2x-1)^2 – 7(x+3)(x-3)=36 c) (x-1)(x^2 + x + 1) + x(x+2)(2-x) =

Tháng Sáu 26, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: Tìm x biết:
a) 6(x+2)(x-3) – 3(x-2)^2 – 3(x-1)(x+1)=1
b) 3(x+2)^2 + (2x-1)^2 – 7(x+3)(x-3)=36
c) (x-1)(x^2 + x + 1) + x(x+2)(2-x) =5
d) (x-1)^3 – (x+3)(x^2 – 3x + 9) + 3(x^2 – 4)=2

Comments ( 1 )

  1. dongoctuan
    dongoctuan
    26 Tháng Sáu, 2022 at 8:46 chiều
    Reply
    Giải đáp:
     $a) 6.(x+2).(x-3)-3.(x-2)²-3.(x-1).(x+1)=1$
    $⇔ (6x+12).(x-3)-3.(x²-4x+4)-3.(x²-1)=1$
    $⇔ 6x²-18x+12x-36-3x²+12x-12-3x²+3=1$
    $⇔ (6x²-3x²-3x²)+(12x+12x-18x)+(3-36-12)=1$
    $⇔ 6x-45=1$
    $⇔ 6x= 46$
    $⇔ x=\dfrac{23}{3}$
    $Vậy$ $x=\dfrac{23}{3}$
    $b) 3.(x+2)²+(2x-1)²-7.(x+3).(x-3)=36$
    $⇔ 3.(x²+4x+4)+4x²-4x+1-7.(x²-9)=36$
    $⇔ 3x²+12x+12+4x²-4x+1-7x²+63=36$
    $⇔ (3x²+4x²-7x²)+(12x-4x)+(12+1+63)=36$
    $⇔ 8x+76=36$
    $⇔ 8x= -40$
    $⇔ x=-5$
    $Vậy$ $x=-5$
    $c) (x-1).(x²+x+1)+x.(x+2).(2-x)=5$
    $⇔ x³-1+(x²+2x).(2-x)=5$
    $⇔ x³-1+2x²-x³+4x-2x²=5$
    $⇔ (x³-x³)+(2x²-2x²)+4x-1=5$
    $⇔ 4x-1=5$
    $⇔ 4x=6$
     $⇔ x=\dfrac{3}{2}$
    $Vậy$ $x=\dfrac{3}{2}$
    $d) (x-1)³ – (x+3).(x²-3x+9)+3.(x²-4)=2$
    $⇔ x³-3x²+3x-1-x³-27+3x²-12=2$
    $⇔ (x³-x³)+(3x²-3x²)+3x-(1+27+12)=2$
    $⇔ 3x-40=2$
    $⇔ 3x=42$
    $⇔ x= 14$
    $Vậy$ $x=14$

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

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