Đáp án+Giải thích các bước giải:

`9, (x+3)^2 \ne 0 => x+3 \ne 0 => x \ne -3`

`10, (4+x)^3 \ne0 => 4+x \ne0 =>x\ne-4`

`11, 4x^2 + 4x +1 \ne 0 => (2x+1)^2 \ne 0 => 2x +1 \ne 0 => x \ne -1/2`

`12, x^2 -x +1 \ne 0 => (x-1/2)^2 + 3/4 \ne 0`

`13, 2x^2 - 6x \ne 0 => 2x(x-3)\ne => x\ne0 , x\ne3`

`14, 2x - 3x^2 \ne0 => x(2 - 3x)\ne 0 => x \ne0 , x \ne 2/3`

`15, 9x^2 - 4y^2 \ne 0 => (3x-2y)(3x+2y) \ne 0 => 3x \ne +-2y => x \ne(+-2y)/3 => 2y \ne +-3x => y \ne (+-3x)/2`

`16, 4x^2 -1 \ne 0 => (2x-1)(2x+1) \ne 0 => 2x \ne +-1 => x \ne (+-1)/2`