What is the domain of

x^2-x-6

x^2-9x+18

Domena is a set of arguments , the value x. 

We need to reject SUCH values of x , which must not be used . We know that you can not divide by zero , so the denominator can not equal zero.

We compute what value of x will give us the denominator 0

x² - 9x + 18 = 0
a = 1  , b= -9   , c=18   - coefficients
discriminant of a quadratic equation

Δ = b² - 4*a*c = (-9)² -4 * 1 * 18 = 81 - 72 = 9   ⇔ √Δ = 3

zeros of functions



D = R/ {3,6}

Just turn the whole gym into pie