Step-by-step explanation:
This is most easily solved by writing the factored form:
[tex]f(x) = (x + 9)(x + 1)[/tex]
Notice how, if we were to substitute -9 for x, the left part would be -9 + 9 = 0. Since (x + 1) × 0 = 0, this makes the function 0. The same logic applies for the right part.
