The roots of the function f(x) = x2 – 2x – 3 are shown. What is the missing number?

so then what are you asking?

step-by-step explanation:

or

step-by-step explanation:

we need to solve for 'x' the following equation:  

we have that:

⇒

⇒ ⇒

factorizing, we get that:

  ⇒

then, the solutions are: or

nothing extraneous has been found!