1.
If the domain of the function f(x)=log7(1log4(x29x+18))f(x) = \log_7(1 - \log_4(x^2 - 9x + 18)) is (α,β)(γ,δ)(\alpha, \beta) \cup (\gamma, \delta), then α+β+γ+δ\alpha + \beta + \gamma + \delta is equal to: