Question

mn giúp mình với ạa

Answer 1

`#3107.101107`

2.

a)

`(x - 2y)^2 = x^2 - 2*x*2y + (2y)^2 = x^2 - 4xy + 4y^2`

`=> -2xy -> -4xy`

b)

`(4a + 3b)^2 = (4a)^2 + 2*4a*3b + (3b)^2 = 16a^2 + 24ab + 9b^2`

`=>` `a^2 -> 16a^2`; `b^2 -> 9b^2`

c)

`9x^2 + 6xy + y^2 = (3x)^2 + 2*3x*y + y^2 = (3x + y)^2`

`=>` `(3x - y)^2 -> (3x + y)^2`

d)

`(a - 2b)^3 = a^3 - 3*a^2*2b + 3*a*(2b)^2 - (2b)^3 = a^3 - 6a^2b + 12ab^2 - 8b^3`

`=>` `-8a^2b -> -6a^2b`; `6ab^2 -> 12ab^2.`