The roots of the function f (x) = x^2-2x-3are shown. What is the missing number

x = - 1 or x = 3 are the roots

to find the roots equate f (x) to zero

x² - 2x - 3 = 0

(x - 3) (x + 1) = 0 ← factored form

equate each factor to zero and solve for x

x - 3 = 0 ⇒ x = 3

x + 1 = 0 ⇒ x = - 1