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

Toán Lớp 8: Tính (vận dụng hằng đẳng thức) a. (x – 2y)^2 b. (2x^2 + 3)^2 c. (x – 2)(x^2 + 2x + 4) d. (2x – 1)^3

Toán Lớp 8: Tính (vận dụng hằng đẳng thức)
a. (x – 2y)^2
b. (2x^2 + 3)^2
c. (x – 2)(x^2 + 2x + 4)
d. (2x – 1)^3

Comments ( 2 )

  1. a) (x-2y)^2
    = x^2 -2.x.2y-(2y)^2
    = x^2 -4xy-4y^2
    b) (2x^2 +3)^2
    = (2x^2)^2 +2.2x^2 .3 +3^2
    = 4x^4 +12x^2 +9
    c) (x – 2)(x^2 + 2x + 4)
    = (x-2)(x^2 +x.2 +2^2)
    = x^3 -2^3
    = x^3 -8
    d) (2x-1)^3
    = (2x)^3 -3.(2x)^2 .1+3.2x.1^2 -1^3
    = 8x^3 -12x^2 +6x -1

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

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