Question

Bài 20: Điền hàng tử thích hợp vào chỗ có dấu * để có hằng đẳng thức:

c) x² + x + * = (* + *)²

d) * - 2a + 4 = (* - *)²

e) 4y² - * = (* - 3x)(* + *)

f) * - \(\dfrac{1}{4}\)= (3y - *)(* + *)

g) 8x³ + * = (* + 2a)(4x² - * + *)

h) * - 27x³ = (4x - *)(9y² + * + *)

i) * + * = (* + \(\dfrac{1}{2}\)y)(4x² - * + *)

j) * - * = (4y - *)(* + y + *)

k) 64a³ + * + * + 27b³b = (* + *)³

l) 8a³ - * + * - * = (* - 3y)³

m) (* - *)³ = x³ - * + 12xy² - *

n) (* + *) = * + 108x²y + 144xy² + *

Answer 1

c)\(x^2+x+\dfrac{1}{4}=\left(x+\dfrac{1}{2}\right)^2\)

d)\(\dfrac{a^2}{4}-2a+4=\left(\dfrac{a}{2}-2\right)^2\)

e) \(4y^2-9x^2=\left(2y-3x\right)\left(2y+3x\right)\)

f)\(9y^2-\dfrac{1}{4}=\left(3y-\dfrac{1}{2}\right)\left(3y+\dfrac{1}{2}\right)\)

g)\(8x^3+8a^3=\left(2x+2a\right)\left(4x^2-4xa+4a^2\right)\)