## Algebra and Trigonometry 10th Edition

All the real numbers except $x=-2$ and $x=-4$.
$\frac{x^2-5x+6}{x^2+6x+8}$ The denominator can not be equal to zero: $x^2+6x+8\ne0$ $x^2+4x+2x+8\ne0$ $x(x+4)+2(x+4)\ne0$ $(x+2)(x+4)\ne0$ $x\ne-2$ and $x\ne-4$