Question

What is the domain of

f(x) = √(x^2-2x-8)

Thanks!

Answer 1

When the leading coefficient a is positive, the parabola opens up ( concave up )

For function:

x ^ 2 - 2 x - 8

the leading coefficient is a = 1

function is concave up

When the parabola ia concawe up all walues between roots are negative.

No negative number can have a real square root.

Funtions zerro points are :

- 2 and 4

So domain of your function:

( - infinity , -2 ] U [ 4 ,infinity )

OR

x <= -2 and x >= 4


If you don't knowe how to solve equation:

x ^ 2 - 2 x - 8 = 0

In google type:

quadratic equation online

When you see list of results click on:

Free Online Quadratic Equation Solver:Solve by Quadratic Formula

When page be open in rectangle type:

x ^ 2 - 2 x - 8 = 0

and click option: solve it!

You wil see solution step-by-step


If you want graph of functions:

Go on :

wolframalpha dot com

When page be open in rectangle type :

x ^ 2 - 2 x - 8

and click option =

after few seconds yo will everythig about function

Then type :

sqrt ( x ^ 2 - 2 x - 8 )

and click option =


P.S.

Sorry for My bad English