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

Toán Lớp 8: khai triển hằng đẳng thức để tính a, 4 – y^6/9 b, 25x^6 – 4y^2/49 c, 27x^3 – 1/8

Tháng Hai 11, 2023 Toán học 2 Comments 0 views

Toán Lớp 8: khai triển hằng đẳng thức để tính
a, 4 – y^6/9
b, 25x^6 – 4y^2/49
c, 27x^3 – 1/8

Comments ( 2 )

  1. lanminhngoc
    lanminhngoc
    11 Tháng Hai, 2023 at 7:14 chiều
    Reply
    ~rai~
    \(a)4-\dfrac{y^6}{9}\\=2^2-\left(\dfrac{y^3}{3}\right)^2\\=\left(2+\dfrac{y^3}{3}\right)\left(2-\dfrac{y^3}{3}\right).\\b)25x^6-\dfrac{4y^2}{49}\\=(5x^3)^2-\left(\dfrac{2y}{7}\right)^2\\=\left(5x^3+\dfrac{2y}{7}\right)\left(5x^3-\dfrac{2y}{7}\right).\\c)27x^3-\dfrac{1}{8}\\=(3x)^3-\left(\dfrac{1}{2}\right)^3\\=\left(3x-\dfrac{1}{2}\right)\left[(3x)^2+3x.\dfrac{1}{2}+\left(\dfrac{1}{2}\right)^2\right]\\=\left(3x-\dfrac{1}{2}\right)\left(9x^2+\dfrac{3}{2}x+\dfrac{1}{4}\right).\)
     

  2. tongtung
    tongtung
    11 Tháng Hai, 2023 at 7:13 chiều
    Reply
    a)4-(y^6)/9=2²-((y^3)/3)^2=(2+(y^3)/3)(2-(y^3)/3)
    b)25x^6-(4y²)/49=(5x³)^2-((2y)/7)^2=(5x³+(2y)/7)(5x³-(2y)/7)
    c)27x³-1/8
    =(3x)³-(1/2)^3
    =(3x-1/2)[(3x)²+3x. 1/2+(1/2)^2]
    =(3x-1/2)(9x²+3/2x+1/4)
     

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

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