Question

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Answer 1

[Kiều Vũ Linh]

Bài 2

a) A = (-2x²y² + 4xy - 6xy³) : 2xy

= -xy + 2 - 3y²

Thay x = 1/2; y = 4 vào A, ta có:

A = -1/2 . 4 + 2 - 3 . 2²

= -2 + 2 - 12

= -12

b) B = 25x² - 10xy² + y⁴

= (5x - y²)²

Thay x = 2; y = 3 vào B, ta có:

B = (5.2 - 3²)²

= (10 - 9)²

= 1²

= 1

c) C = (3x + 2)² + 2(3x + 2)(2y - 1)² + (2y - 1)²

= (3x + 2 + 2y - 1)²

= (3x + 2y + 1)²

Thay x = 1/3; y = -1/2 vào C, ta có:

C = [3 . 1/3 + 2 . (-1/2) + 1]²

= (1 - 1 + 1)²

= 1²

= 1

Answer 2

[Kiều Vũ Linh]

Bài 3

a) x³ + 2x² = x²(x + 2)

b) 3(x - y) - 5x(y - x)

= 3(x - y) + 5x(x - y)

= (x - y)(3 + 5x)

c) 4x³ - 9x

= x(4x² - 9)

= x(2x - 3)(2x + 3)

d) (x - 2y)² - 4(x + y)²

= (x - 2y)² - [2(x + y)]²

= (x - 2y) - (2x + 2y)²

= (x - 2y - 2x - 2y)(x - 2y + 2x + 2y)

= (-x - 4y).3x

= -3x(x + 4y)

e) x²y + x² - 4y - 4

= (x²y + x²) - (4y + 4)

= x²(y + 1) - 4(y + 1)

= (y + 1)(x² - 4)

= (y + 1)(x - 2)(x + 2)

f) -27x³(x + 1) + x + 1

= - 27x³(x + 1) + (x + 1)

= (x + 1)(-27x³ + 1)

= (x + 1)(1 - 27x³)

= (x + 1)(1 - 3x)(1 + 3x + 9x²)